RoadTest: E36313A Triple Output DC P.S.
Author: rachaelp
Creation date:
Evaluation Type: Power Supplies
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: There are numerous power supplies available from all the main test equipment manufacturers. The most direct comparison product I have available is a TTi QL335T or alternatively I have a TTi PL303QMD + TTi CPX400S combo, both of these solutions would give comparable triple PSU outputs.
What were the biggest problems encountered?: The unit being shipped with the wrong configuration but this isn't really a problem as it's easy to solve. I have found that there is an audible mains hum from my unit regardless of whether the supply is turned on or off, for as long as the AC inlet is powered. From searching online I found that whilst most people report the unit to be extremely quiet, there are some people who have units which make a mains hum the same as my unit. I reported the issue to Randall and he contacted Keysight who have sent me an email this morning confirming that this is not normal for these units and they are going to send me a replacement unit and arrange for my current one to be collected so they can investigate the issue. This is excellent service from Element14/Keysight.
Detailed Review:
I received my shiny new Keysight E36313A Power Supply from Element14 this week. Thank you so much to both Element14 and Keysight for picking me for this Road Test. It's an excellent product and I am very happy indeed to have one sitting in my lab. I have a pretty good setup already but my current PSU's are missing a few really useful features which the Keysight unit happily provides.
This Power Supply is the top of the range model from the Keysight E36300 range. There are three models currently available, the entry level E36311A which is limited to 80W total power output and has a limited feature set, and the fully featured E36312A and E36313A models which have all the features enabled but with 80W and 160W total output power respectively. These models can also optionally have a GPIB interface which is supplied in my review unit. Unfortunately I do not have any way to utilize GPIB currently, but as the unit also has USB and Ethernet this is no problem at all. The main differentiations between the available features for the three models is shown in the image* below:
* Taken from the Keysight E36313A Bench Power Supply Data Sheet
Keysight E36300 Triple Output Bench Power Supply Data Sheet: http://literature.cdn.keysight.com/litweb/pdf/5992-2124EN.pdf
The unit came very well packed in a sturdy box and held firmly in place within the box with custom packaging. Inside the box was the E36313A itself and a small box containing the following additional items:
The main specifications for the three versions available of the Keysight E36300 Bench Power Supplies shown in the image* below:
* Taken from the Keysight E36313A Bench Power Supply Data Sheet
For this road test I am going to be evaluating the Keysight E36313A and comparing it to two other solutions I have available to me:
Specification | Keysight E36313A | TTi QL355T TTi QL355TP | TTi PL303QMD TTi PL303QMD-P | TTi CPX400S TTi CPX400SP |
---|---|---|---|---|
Price* * As on Farnell UK 18/12/2017 | £1317.00 + VAT | £760.00 + VAT £947.00 + VAT | £529.00 + VAT £707.00 + VAT | £558.00 + VAT £717.00 + VAT |
DC Output Ratings | Channel 1: 0 to 6V @ 0 to 10A Channel 2: 0 to 25V @ 0 to 2A Channel 3: 0 to 25V @ 0 to 2A Channel 2||3: 0 to 25V @ 0 to 4A Channel 2+3: 0 to 50V @ 0 to 2A | Channel 1: 0 to 15V @ 0 to 5A / 0 to 35V @ 0 to 3A / 0 to 35V @ 500mA Channel 2: 0 to 15V @ 0 to 5A / 0 to 35V @ 0 to 3A / 0 to 35V @ 500mA Channel 3: 2.7V @ 0 to 1A / 3.3V @ 0 to 1A / 5V @ 0 to 1A | Channel 1: 0 to 30V @ 0 to 3A Channel 2: 0 to 30V @ 0 to 3A Channel 1||2: 0 to 30V @ 0 to 6A | 0 to 60V @ 0 to 20A (Max 420W TPD) |
Max Total Power | 160W | 110W | 180W | 420W |
Operating Modes | Independent, Tracking, Series*, Parallel* * Fully automatic connection and control | Independant, Linked*, Tracking * Enables linked controls with manually configured series / parallel modes | Independant, Tracking, Series*, Parallel* *Series with manual connection in Tracking mode, Parallel is configured internally with a switch on the front panel. | Independant |
Load Regulation - Voltage | < 0.01% + 4 mV | Channel 1: < 0.01% + 2 mV Channel 2: < 0.01% + 2 mV Channel 3: < 1.0% for a 90% load change | Channel 1: Channel 2: | < 0.01% |
Load Regulation - Current | < 0.01% + 500 uA | Channel 1: < 0.01% + 250uA (5A/3A range), < 0.01% + 50uA (500mA range) Channel 2: < 0.01% + 250uA (5A/3A range), < 0.01% + 50uA (500mA range) Channel 3: < 1.0% for a 90% load change | Channel 1: Channel 2: | < 0.05% |
Line Regulation - Voltage | < 0.01% + 1 mV | Channel 1: < 0.01% + 2mV for a 10% line change Channel 2: < 0.01% + 2mV for a 10% line change Channel 3: < 0.1% for a 10% line change | Channel 1: Channel 2: | < 0.01% for a 10% line change |
Line Regulation - Current | < 0.01% + 500 uA | Channel 1: < 0.01% + 250uA (5A/3A range), < 0.01% + 50uA (500mA range) Channel 2: < 0.01% + 250uA (5A/3A range), < 0.01% + 50uA (500mA range) Channel 3: < 0.1% for a 10% line change | Channel 1: Channel 2: | < 0.01% for a 10% line change |
Output Ripple | Channel 1: < 350 uVrms / 2 mVpp Channel 2: < 1 mVrms / 5 mVpp Channel 3: < 1 mVrms / 5 mVpp | Channel 1: < 350 uVrms / 2 mVpp Channel 2: < 350 uVrms / 2 mVpp Channel 3: < 1 mVrms typical | Channel 1: < 400 uVrms / 2 mVpp Channel 2: < 400 uVrms / 2 mVpp | < 3 mVrms / 15 mVpp |
Ethernet | Yes | No | Yes (P version) | Yes (P version) |
USB | Yes | Yes (P version) | Yes (P version) | Yes (P version) |
GPIB | Yes | Yes (P version) | Yes (P version) | Yes (P version) |
RS-232 | No | Yes (P version) | Yes (P version) | Yes (P version) |
So we can see from the above whilst the solutions are comparable in some respects, there are differences which may make one solution or another a better fit for certain applications. For example, the combination of the TTi PL303QMD-P and the TTI CPX400SP give a massive total power capability of 600W between the two which for some higher power applications may be an advantage.
However, it should be noted that it's not all about the fine detail of the specs, a huge factor for a general purpose lab power supply is the ease of use and its ability to be well integrated into an overall test solution. We can see from the above that making various configurations for the output power rails is much simpler with the Keysight as all the connections as well as the combining of controls is all handled internally to the power supply with no additional wiring necessary.
3.2. Rear Panel Overview
The unit is easily configurable to support different voltages. As you can see there is a table on the back showing the switch positions for 100V, 115V, and 230V. In my case I simply needed to slide the right hand switch over from the left to the right to change it to the correct setting. Below is a close up on this section of the rear panel to give a clearer view of the configuration switches. So, a small disaster has been averted and I can get on with reviewing my unit!
In the words of Dave Jones from the EEVBlog (like you didn't know who he was?!), don't turn it on, take it apart!
Okay so I'm not Dave Jones, or any of those that get given lots of free kit with the explicit expectation they'll tear it down. I'm not going to totally strip the unit down into as many pieces as I can get it into now because I don't want to risk accidentally damaging the unit and I really like this unit and want to be able to use it as my main lab power supply so I am not going to do anything to risk breaking it. If Keysight would like to send me a faulty unit they have lying around, I would be more than happy to do a more detailed tear down of that at a later date, but for now I'm just going to pop the lid and take a few pics of the insides. It's quite easy to get the lid off if you have a Torx driver set as it is held in place by two Torx bolts on each side and two on the top at the back. Once these are removed the lid simply slides out backwards.
So the big question is, how well does this interface work for every day usage scenarios. Well, I've only had it a couple of days so haven't used it extensively at all yet but it seems very intuitive to use. The combination of a simplified single set of controls to operate all three channels, the colour coding and the very large and clear colour LCD give a good foundation for a easy to operate unit. Lets now take a short tour around a few of the menus to see how we'd go about setting up the unit to perform a few basic tasks. We'll do this by way of some examples which we will work through to show the various steps required.
So before we get into the actual setups, I wanted to show you a image of the main screen and show a little glitch I found when using the web interface (we'll look at this later) to grab images from the screen.
Looking at the two images above, these are both of the main LCD screen when it just has the default configuration of 0V and maximum current set up on all it's outputs.
If you look carefully you will see that on the first image there is a glitch in the current reading for both channel 1 and channel 2. These are reading exceedingly small values, in the order of <10uA and there is naturally some noise on these readings. However, you'd expect the capture to grab a stable image. It would appear rather than the capture grabbing the currently stable display buffer it is grabbing a buffer that is the subject of the next display update. I don't know if the rendering to the display itself is double buffered or not, although I haven't seen any tearing on the display which is the usual sign of updates happening on the live display, but this issue with the screen capture is something to watch out for if you are grabbing images for a report. It means rather than working through quickly and grabbing all the images you need as you go, you have to switch to another window and check the grabbed image and recapture if necessary. I hope Keysight fix this issue soon!
In the screen captures you can see the information about each channel which is displayed, i.e. The set voltage and current, the actual measured voltage and current, whether a 2-Wire or 4-Wire connection is used, and whether the channel is turned on or off. If I now press the Channel 1 select button again the display will change to give more detailed information for Channel 1 as shown below.
Above I made a brief comment about showing whether 2-Wire or 4-Wire output modes are being used. In case you are not familiar with this terminology, I will explain further now.
Those with eagle eyes (or generally anybody who has got this far and been paying attention!) will notice that the front panel doesn't have the capability available for 4-Wire connections. If you wish to use this mode of operation then you will need to make some cables up with the supplied terminal plugs and use the rear panel connectors.
I had intended to take a look at how this supply integrates into KeySights BenchVue instrument control and automation suite. However, upon launching my Windows 10 virtual machine where I had previously installed an used the software I found it had disappeared which is totally weird. I then downloaded the installer for the latest BenchVue 2017 and tried to reinstall it and finally after about 4 hours it appeared to complete the installation, however upon looking for anything relating to BenchVue being installed I found almost nothing except for the BenchVue FieldFox app, none of the other apps and not the main application. Again, this was totally weird and disappointing. Fortunately I was able to resurrect a Windows 7 virtual machine from elsewhere and I found on this that BenchVue 2017 installed quite happily and comparatively quickly. Happy days!
Unfortunately the happy feeling only lasted a short while. After loading the latest version of BenchVue I found that the majority of the modules for it are now only available at cost with the addition of Pro licenses. This is not a change I particularly like as the earlier version of BenchVue I had gave access to feature limited versions of the various modules so you could at least get a feel for its operation. I have this power supply, my oscilloscope and my multimeter, all of which are separate modules so the cost to buy these is significant. There is a trial version available for each of these but as I don't know how I might wish to use this yet I don't want to start the trial until such time as I am ready to invest some serious time into investigating and setting up BenchVue.
BenchVue Software 2017 Technical Overview: http://literature.cdn.keysight.com/litweb/pdf/5991-3850EN.pdf
BenchVue Software 2017 Platform Website: https://www.keysight.com/main/software.jspx?ckey=2417463
The first thing I noticed when I powered up the unit was that even though it's a smart power supply with a processor running a network stack and providing a web interface and various programmable options, as well as supporting a modern user interface with a large LCD, it powers up and is ready to use within just a few seconds. Below is a video showing the overall boot up speed of the unit.
So as you can see, from me starting the camera recording, pressing the button to switch on the power supply to me stopping the recording, it's only 10 seconds in total, the power supply booting up is only a few of those seconds which is very nice. Nice one Keysight!
For this test I am going to use my DC electronic load which is a TTi LD300. This can support up to 80V input and up to 80A within a total power dissipation of 300W. For testing the outputs of the Keysight E36313A I will use the 80A constant current range to enable me to load Channel 1 of the power supply to 10A and I will use the 8A constant current range to load Channel 2 and Channel 3 of the power supply in their various independent, series, and parallel modes.
The following tests are going to be performed on the Keysight E36313A only as we can assume that the TTi units perform to their load specs. I have used these for a number of years and I know they work as advertised in this respect.
Keysight E36313A Configuration | Keysight E36313A Results | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
The voltage of the channel was set to 25V and the current limit was set to 2A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 2A.
| |||||||||||||||
The voltage of the channel was set to 25V and the current limit was set to 2A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 2A.
|
Keysight E36313A Configuration | Keysight E36313A Results | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Channels 2 and 3 were put into serial mode and the voltage of the combined channel was set to 50V and the current limit was set to 2A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 2A.
|
Keysight E36313A Configuration | Keysight E36313A Results | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Channels 2 and 3 were put into parallel mode and the voltage of the combined channel was set to 25 and the current limit was set to 4A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 4A.
|
Testing under various loads with the maximum voltages available on each channel and the Keysight E36313A didn't miss a beat. It works as expected and was very easy to reconfigure for each test.
This this test I am just going to compare the Channel 1 output of the Keysight E36313A with the TTi CPX400S and the Channel 2 output with Channel 1 of the TTi PL303QMD. I'll take a look at the ripple and stability of each of the outputs on my Keysight MSOX3054A Oscilloscope using an AC coupled voltage probe when loaded up the outputs with my TTi LD300 electronic load. I will used the web interface available with the LAN Option for the Oscilloscope to capture the resulting waveforms.
Keysight E36313A Configuration | Keysight E36313A Results | TTi CPX400S Results |
---|---|---|
Keysight E36313A Configuration | Keysight E36313A Results | TTi CPX400S Results |
---|---|---|
Keysight E36313A Configuration | Keysight E36313A Results | TTi CPX400S Results |
---|---|---|
Keysight E36313A Configuration | Keysight E36313A Results | TTi PL303QMD Results |
---|---|---|
Keysight E36313A Configuration | Keysight E36313A Results | TTi PL303QMD Results |
---|---|---|
Keysight E36313A Configuration | Keysight E36313A Results | TTi PL303QMD Results |
---|---|---|
We can see from the results that all three supplies are very good. The Keysight E36313A has strong performance in all the tests, beating the TTi CPX400S in the transient load and output noise measurements, where the TTi CPX400S had some noticeable regular switching spikes which increased with current. At the higher voltage and lower current tests the Keysight E36313A performed roughly on a par with the TTi PL303QMD, having slightly more excursion low but slightly less excursion high on the transient voltage test.
Under 200ma/2A transient load test the TTi power supply would run but would occasionally trip even though I had actually set the current limit to a little over 2A. They Keysight E36313A did not trip out during this test at all.
For this test I will look at just the single output with 1A and 10A load conditions setup from the previous tests and using the FFT function of my Keysight MSOX3054A I will attempt to see if there are any noticeable peaks in the spectrum which are dependant on load which are detectable within the capabilities of my oscilloscope. I will used the web interface available with the LAN Option for the Oscilloscope to capture the resulting waveforms.
Keysight E36313A Configuration | Keysight E36313A Results | TTi CPX400S Results |
---|---|---|
Keysight E36313A Configuration | Keysight E36313A Results | TTi CPX400S Results |
---|---|---|
Looking at the results we can see that the TTi CPX400S has got a higher peak at 125MHz and additional spurs at 187.5MHz, 200MHz, 212.5MHz and 225MHz which are either not present or at a much lower level on the output of the Keysight E36313A. These likely correlate with the edge speed of the switching noise we saw in the previous output noise tests but without further investigation I cannot be sure.
We can also see from the FFT that there are spurs in the 85MHz to 105MHz range for all tests and all equipment. These are present even under no load and with the output disabled on both units, I think these are actually artefacts which are caused by some digital data being picked up from elsewhere. I haven't tracked down from exactly where yet but if we look at the following images you can see the regularity of the bursts and with the zoomed image we can see something which looks like it might be in the 20MHz-25MHz range. It's obviously very hard to see the details of the data streams from a spurious waveform captured on my oscilloscope.
For this test I will be capturing a set of data over time and recording it to a file which I will then import into a spreadsheet application to perform some graphing of the results. I have chosen to log the Voltage, Current and Power measurements when booting up a Raspberry Pi Model B and running some benchmark tests. For my tests I will be performing 5 separate actions
sysbench --test=cpu --cpu-max-prime=2000 run
sysbench --test=memory run --memory-total-size=2G
sysbench --test=memory run --memory-total-size=2G --memory-oper=read
sudo shutdown -HP now
The unit comes with a relatively straight forward to use data logger. You can configure what values are captured, i.e. V/I/P from Channels 1/2/3, you can configure how long it captures for, how often it samples the data etc. As it's logging it will show you the waveform of the log in a graph which is like a little oscilloscope with a slow time base. You need a USB stick to capture the data and you can save it in a binary dlog format and also in CSV format.
The following image shows the log view of the data collected:
I also captured the log data into a CSV file:
E36313A exported datalog File type: CSV "Sample interval: 0.200000" "Number of sample: 1026/1650" "Trigger sample: 0" "Date: 2017/12/19 14:28:28" "V1: 5.000000, -7.500000" "I1: 0.200000, 0.150000" "P1: 1.000000, 2.781250" "V2: 5.000000, 0.000000" "I2: 1.000000, 0.000000" "P2: 2.000000, 0.000000" "V3: 5.000000, 0.000000" "I3: 1.000000, 0.000000" "P3: 2.000000, 0.000000" Sample,"Volt avg 1","Curr avg 1" 0,0.001310,0.000070 1,0.001310,0.000070 2,0.001310,0.000070 3,0.001310,0.000070 4,0.001310,0.000070 5,0.001310,0.000070 6,0.001310,0.000070 7,0.001310,0.000070 8,4.999190,0.084240 9,5.000390,0.113180 10,5.000590,0.095300 11,5.000590,0.076760 12,5.000590,0.102770 13,5.000590,0.098550 14,5.000590,0.067660 15,5.000590,0.098220 16,5.000590,0.104070 17,5.000590,0.107650 18,5.000590,0.082940 19,5.000790,0.067330 20,5.000590,0.067330 21,5.000590,0.067330 22,5.000590,0.067330 23,5.000590,0.074490 24,5.000590,0.127810 25,5.000590,0.127810 26,5.000590,0.128130 27,5.000590,0.121630 28,5.000590,0.141140 29,5.000590,0.111550 30,5.000590,0.149920 31,5.000590,0.156750 32,5.000590,0.157070 33,5.000590,0.115780 34,5.000590,0.115780 35,5.000590,0.115780 36,5.000590,0.115780 37,5.000590,0.187960 38,5.000590,0.227950 39,5.000790,0.194140 40,5.000590,0.242910 41,5.000590,0.259490 42,5.000590,0.281270 43,5.000590,0.288100 44,5.000590,0.277040 45,5.000590,0.278350 46,5.000590,0.277690 47,5.000590,0.278020 48,5.000590,0.262410 49,5.000590,0.323210 50,5.000590,0.279970 51,5.000590,0.280950 52,5.000790,0.307280 53,5.000790,0.280950 54,5.000590,0.269570 55,5.000790,0.271190 56,5.000590,0.270220 57,5.000790,0.255590 58,5.000590,0.260460 59,5.000590,0.267940 60,5.000790,0.280620 61,5.000790,0.250060 62,5.000790,0.264690 63,5.000590,0.261110 64,5.000590,0.251360 65,5.000590,0.251360 66,5.000590,0.251030 67,5.000790,0.258190 68,5.000790,0.249730 69,5.000590,0.262740 70,5.000590,0.261440 71,5.000790,0.253640 72,5.000590,0.259810 73,5.000590,0.278350 74,5.000790,0.240300 75,5.000590,0.251030 76,5.000790,0.266640 77,5.000590,0.253960 78,5.000590,0.258190 79,5.000590,0.254940 80,5.000790,0.267290 81,5.000590,0.251030 82,5.000590,0.259160 83,5.000590,0.246810 84,5.000590,0.262090 85,5.000590,0.252330 86,5.000790,0.257210 87,5.000790,0.252010 88,5.000790,0.251360 89,5.000790,0.253640 90,5.000590,0.254940 91,5.000590,0.245830 92,5.000590,0.235430 93,5.000590,0.234780 94,5.000790,0.235430 95,5.000590,0.237380 96,5.000590,0.271520 97,5.000590,0.247130 98,5.000590,0.235430 99,5.000590,0.235430 100,5.000790,0.252010 101,5.000590,0.236730 102,5.000790,0.250060 103,5.000790,0.252010 104,5.000790,0.260790 105,5.000790,0.250060 106,5.000590,0.254610 107,5.000590,0.256890 108,5.000590,0.278020 109,5.000790,0.257210 110,5.000590,0.245830 111,5.000790,0.258840 112,5.000590,0.250380 113,5.000590,0.252010 114,5.000590,0.238030 115,5.000590,0.249730 116,5.000590,0.254940 117,5.000790,0.239980 118,5.000590,0.252980 119,5.000790,0.250380 120,5.000590,0.236400 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For some reason it has not included the logged power data in the CSV file. I need to investigate why this is the case. It's not actually an issue as we can reconstruct the power from the V and I data, which I will do in excel with a simple formula.
Once you have the data in a useful format there are many things you could so with it depending upon what the data represents. The simplest thing you can do is simply graph the data in Excel or Open/LibreOffice Calc (other Spreadsheets are available too, just use whatever you like and/or are familiar with). The following is a graph of the current (blue trace) and calculated power (red trace) for the experiment of booting up the Pi and running various benchmarks.
Using such tools you could easily calculate the average power consumption of a piece of equipment over time, or correlate particular operations happening on the hardware or in the software with peaks in power consumption, which, if you are designing something that is required to run on batteries and needs to be low power, this can give some real insights into where to target your efforts in the design to get the best performance for the lowest power consumption.
You could of course bring the data into more comprehensive tools like MatLab, Octave, etc or write your own custom tools to process the data specific for your needs.
UPDATE 21/12/2017:
I've been experimenting and using the logging a little more and it really is very useful and as dougw shows in one of the videos in his road test, there are plenty of more creative ways to make use of the logger. I have found a few limitations though which I think could be improved upon.
Firstly, when you set the logging period for an extended time, it gets to a point where is says there is not enough device memory and it starts to increase the logging interval. Why is this? If I am logging to a say 16Gb USB stick why am I restricted to the log size based upon memory available within the power supply itself? I would have thought even if it needs to use internal memory to capture the initial data, flushing this data to a file periodically should allow this to be able to continuously log until the USB is full. I hope this is something that can be corrected to allow the logging to be used more effectively for long term experiments.
Secondly, in order to start the logger I have to have a USB stick installed. What if I don't have a USB stick available? The logger then becomes unusable. This is a network connected device so why not have the ability to save to a network location or even use some remote logging server which the unit can connect to easily to store the logs?
Finally, I have noticed some waveform glitches on the display, regularly part of a trace will disappear for a second and then reappear. It's quite distracting having a flashing trace on the log view.
As a quick follow up to the earlier comment about the power trace not making it into the CSV file, I have not discovered the reason for this yet. If it's there as a trace I can enable for logging it should be in the file. Yes, I can create it from the V and I for the trace but if I have a long data set adding that column to my spreadsheet is fiddly and involves lots of scrolling. This should also be fixed. While I still think the logging is a great feature and very welcome, it isn't bug free and does have some limitations so for now I'm going to amend my review score down a point for the bugs and the newly discovered logging limitations. If a new firmware is released that resolves these issues I will report back and amend the score accordingly.
In an ideal world your wires which connect your power supply to your load would have zero or negligible impedance, but in reality there is a small impedance present, usually in the order of a few tens or hundreds of mOhm for typical bench hook up cables. For low current applications this small impedance makes almost no difference and the voltage measured directly at the load is almost identical to the voltage measured at the output of the power supply. As the current increases, using Ohms law (V = I/R) we can soon see how higher currents could lead to a significant drop in the voltage between the source and the load. In order to compensate, if the load was constant you could just raise the source voltage until the load voltage was at the desired level, but this is not a suitable approach as the load could change and you may end up with an over-voltage condition on the input to your load.
Usually the power supply will feed back the voltage it is using to control the output of the supply from as close to the output as possible. This compensates for any losses in the output stage of the supply but does nothing to help the case where there are additional external losses. This is where 4-Wire connections come into play. An additional pair of wires connect from the power supply to the load and these are used as dedicated sense pairs to measure the voltage directly at the load. These sense wires carry none of the output current so there is no current related voltage drop, it's an accurate measurement of the voltage directly at the load. This measurement is used instead (or as well as) of the internal voltage measurement to enable to supply to automatically deliver the desired voltage directly at the load.
Keysight E36313A Configuration | Keysight E36313A Results |
---|---|
With the output set to 2-Wire mode with a 5V output and 6.66A load (as reported on the TTi LD300 DC Electronic Load) the voltage measured on my DMM is 4.428V. This means that in my cabling between the power supply output and the load there is almost over 0.57V dropped. This is plenty to cause issues for test devices which require 5V +/-10%.
Update 20/12/2017: Having thoroughly investigated my strange readings I have discovered there was an issue with the measurements on my DMM and the voltages I was reading were not correct. Switching my TTi LD300 into meter display so it shows the voltage it sees on it's input and the current it is sinking, with a 10A load and in 2-Wire mode, the voltage at the input to the load is just 4.05V. If I vary the load the measured voltage varies as expected. | |
So it turns out the optimal test current for my particular the 4-Wire setup to be able to correct back up to exactly 5.000V as measure on my DMM is 6.66A. Above this and the PSU doesn't have enough headroom to be able to recover the voltage drop. But up to this, in my setup and the supply perfectly corrected back to exactly 5.000V.
Now to a slight issue, I then dropped the load to only 1A and the supply now incorrectly gives 5.168V measured on my DMM at the load. I need to do some more investigation on this as this is clearly not correct. I need to double check all my test setup and do some more analysis and see if I can fathom what is happening here.
Update 20/12/2017: As stated above, the readings from my DMM were incorrect. On the TTi LD300 meter view, with a 10A load and 4-Wire connections enabled the reading is now exactly 5.00V. This measurement now remains constant regardless of the load. |
All in all I think this unit is very good. It packs in a lot of features and provides a really nice to use interface to access the features. My unit came with the USB/LAN and GPIB interfaces to connect with other systems easily and this opens up a whole lot of additional possibilities. I initially knocked off a couple of points in the "Performed to Expectations" section, one because of the mains hum from my unit, and one for the little niggles I discovered in the UI. Keysight will hopefully provide a firmware update to fix the UI issues at some point. With their response regarding the hum issue and their prompt action to replace my unit I am adding back the point I deducted for this as it appears to be specific to my unit and they are in the process of resolving the issue for me.
In comparison to the TTi units I already have you can see that it performs well. To be fair to TTi, all three unit's are very good but I think the Keysight E36313A out performs the TTi units in a few areas and the user interface and feature set is a deciding factor for me. The output can be seen from the various load tests and FFT's to be a little cleaner and some higher frequency artefacts which are present on the output of the TTi supplies are either not present or much reduced on the Keysight E363213A in comparison.
One thing I can't do with my TTi supplies is easily log data and this is a very valuable tool which the Keysight E36313A makes really easy to use. I can easily log the Voltage, Current, and Power from each of the three channels and then use this data to present these values in a useful and meaningful way or to process the data to extract hidden information such as tracking the overall power consumption of a low power device with many different power states over time.
This concludes my Road Test Review of the Keysight E36313A. Thank you all for reading this review and thanks again to Element 14 and Keysight for choosing me for this Road Test. It has been an honour to receive this item and a pleasure to go through and do a comprehensive review of this excellent piece of equipment. It's now 100% my go to power supply in my lab.
20/12/2017: I've updated the section above regarding the 4-Wire connections to correct my test results and report that is it in fact working well and exactly as expected.
21/12/2017: I've updated the section above regarding the logging capabilities to add my additional findings and limitations.
Top Comments
Hi Rachael,
Thank you for the comprehensive analysis of the power supply. I never dreamed that one could find so much depth to the subject of a power supply.
John
Very good road test report.
Nice look inside, good verification testing and discussion of usability features.
Well done.
DAB
Rachael,
For a first time roadtester, this is real good review. Detailed and I think balanced. The comparison is a good approach for a review. The video and screenshots, with commentary is what we like…