RoadTest: Agilent 34461A Digital Multimeter
Author: Instructorman
Creation date:
Evaluation Type: Independent Products
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?: Tektronix DMM4050
What were the biggest problems encountered?: Really, nothing significant so far.
Detailed Review:
Hello Road Test readers!
I am very happy to be posting the first instalment of my review of the Agilent 344461A 6½ digit multimeter.
I've been exploring this instrument for 8 days. Not enough time to call it an old friend, but enough time to let me know I would be happy to get to know it better.
First impressions
This is a great multimeter. It is, to me, esthetically beautiful, and it matches the form factor and layout of several other recent Agilent instruments. In the photo below you will see a stack of three Agilent instruments. From bottom to top we have the 34461A 6½ digit multimeter, then a 33522B waveform generator (if you are interested, I have posted a Road Test review of this fine instrument here), then a 53230A frequency counter which I bought after being so impressed by the 33522B. Oh, and on top of the whole stack is a Micronta 22-049 from 1972 - that still works, and gives me street credentials as a truly ancient electronics nerd.
The first part of my review is associated with my first blog post on this meter. In the first blog post I look at using the 34461A in trend mode to monitor the drift on a 32.768 kHz real time clock and drift on an Analog Devices AD9835 frequency generator chip. Here in the Road Test section I look at the frequency measurement function on the 34461A and compare it with the same function on the Tektronix DMM4050 6½ digit precision multimeter. Here I also compare the set up and use of limits and trend charts on both meters.
I am experimenting with a combination of text and short video clips in this portion of the review. Hopefully you can get value from either the text or the video, but I think they work well together, each adding an interesting layer of detail. So, let's begin.
The test set up
Initially I set up a configuration on my bench where just about every frequency measuring instrument I've got was connected to the output of a high quality generator. This allowed me to do a quick comparison of all the instruments to get a sense of how well they agreed on a simple measurement of sine wave frequency. The frequency I selected was 32,768 Hz, the ubiquitous RTC reference frequency. This frequency is well within the specs of all the instruments selected for the comparison. As you will see in the short video clip below, three of the four instruments were in essentially perfect agreement. The only dissenter was the Agilent 34461A. The factory fresh 34461A disagreed with the Agilent 53230A, the Tektronix DMM4050 and a Fluke 287 by ½ Hz. Not a lot, but just enough to be a slight annoyance on my first test of this meter.
I am confident the source instrument, a Tektronix AFG3102, is outputting 32,768.00 Hz because the Agilent 53230A frequency counter I used to check the frequency has a TCXO option (temperature controlled crystal oscillator), was calibrated less than six months ago by Agilent, and had been running for four hours before the test was conducted. To keep things fair, the aperture time on the 34461A and the DMM4050 were set to 1s. Check out the video to get a quick tour of the test set up. NOTE: You may have to crank up the volume to hear the audio track. For some of the recording I was behind the camera and the microphone is in front of the camera.
The next two video clips provide a comparision of how test limits are set up in the Tektronix DMM4050 and in the Agilent 34461A. I give my thumbs up vote to Agilent on this comparision. I was only able to establish a ± 1 Hz limit range on the Tektronix, but was able to go to ± 0.1 Hz on the Agilent and could have gone tighter than that. Both instruments, however, would benefit from either a numeric keypad or the ability to connect a keyboard the the front USB port. Either method is superior to using up/down and left/right keys to build up limit values.
Next, I examine the Bar Meter or Bar Graph feature on the Agilent 34461A. This feature caught my attention because is not available on the Tektronix DMM4050 and because I have found that in certain measurement situations an analog bar meter provides a better sense of how a value is changing over short durations when compared to rapidly changing numeric displays. The bar meter feature on the Agilent 34461A is very nice. It is far more than a graphical indication of relative measurement value on a linear scale. It can also provide a graphical history of the range of values experienced by the meter. The hsitory is recorded by a permanent light blue highlight behind the bar meter graphic. When limits are active, the bar meter shows where the limits are relative to the current measured value with pink highlights on either end of the horizontal scale.
I stumbled upon a bit of a shortcoming in the labeling of the bar meter during this experiment. It seems the algorithm that determines the scale markings may not always include sufficient digits to adequetley resolve the displayed scale. In the example shown in the video clip below, the scale covers a range from 32.76847 kHz to 32.76853 kHz, but the low, mid and high tic mark labels read 32.768k, 32.769k and 32.769k. Lack of displayed digits obscures some important fine detail in this case.
In general, I find the inclusion of the bar graph option gives the Agilent 34461A an advantage over the DMM4050, so it gets a thumbs up.
Finally, for this installment of my review, I compare the trend chart function on the 34461A and on the DMM4050. It is interesting and I think important to think about what an instrument is actually telling you. The reason this is important can be seen in the comparision video below where the two meters are in trend mode, looking at the exact same signal, but presenting significantly different graphical interpretations of that signal over time. Both are valid interpretations, but the meaning of each interpretation must be drawn from understanding the method used to derive the graphical interpretation. The more sophisticated the measurement instrument, the greater the need for the user to develop an equally sophisticated understanding of what the instrument is doing and with that understanding, reason when it is, and is not, appropriate to use various measurement features.
Until nest, time. Cheers.
November 3, 2013 update - Web interface and Java UI
In response to requests to review the web interface on the 33461A I have obliged with the following update.
There are six instruments on my bench that support Ethernet connectivity. In the past I would connect a single instrument to my laptop to control the instrument over a network connection. Recently I decided to purchase an 8-port switch and connect the whole lot of them to the laptop on a permanent basis. My experience with network connections to test equipment has been uneven. While all of the Agilent instruments I own connected easily upon first hook up, only one of my Tektronix instruments connected flawlessly on first attempt. Success with Ethernet connection seems to be related to how old the instrument is. The Tektronix MDO4104-3 mixed domain oscilloscope is quite new and it connected without incident on first attempt, as did all three of my Agilent instruments. My two older Tektronix instruments, a DMM4050 multimeter and an AFG3102 arbitrary function generator, did not connect on first try. Although I did not dig deeper, I'm satisfied that the connection problems on the older Tektronix devices are simply a matter of manually tweaking configuration settings.
The range of useful control available through a network connection also varies, it seems, based on the age of the instrument. The interfaces available in the Tektronix MDO4104-3 and the Agilent 34461A are quite full featured, whereas the other Agilent instruments to which I connected (a 53230A counter and a 33522B waveform generator) offer lackluster user interfaces. Now to the details concerning the Agilent 34461A Ethernet interface.
Once a physical connection is made between the port on the back of the instrument and a computer, the user opens a web browser and browses to the device IP address. For the 34461A the device IP address can be obtained through the following keystroke sequence:
Shift+Utility, then I/O config, then LAN settings. On my 34461A this key sequence brings up the display shown below:
I used Firefox 25.0 to browse to the IP address shown in the photograph above. After several seconds, the web page shown below is served:
Clicking on the "Turn On Front Panel Identification Indicator" causes the following screen to appear on the 34461A:
Recall there are six instruments connected to my laptop and this image only appeared on the 34461A, so this feature may come in handy if it becomes necessary to verify a connection when multiple instruments are in play.
Observe Only Mode
Clicking on the instrument icon (second from the top on the left) causes Java to start and may bring up a password dialog, or may not. When I first connected and launched the Java UI I saw a password dialog, which I may have canceled. Since then the password dialog flashes briefly then disappears. After what seems to me to be too long a wait, the following three overlapping windows appear:
Here is where a nice new 24" monitor would come in handy. My laptop has a 15" screen that gets pretty cluttered when this many windows are wedged into the viewing area. The window in back is the main control interface. It has two radio buttons, five other selection buttons and the navigation buttons on the left. The remainder of the window is as open and white as a prairie field in winter. Perhaps not the best use of space. Two dialog windows pop up automatically, the Monitor DMM window and the Control DMM window. These two windows are configured to always be on top - even when you switch applications. So, if I switch to another browser window from the 34461A page, the two windows shown above remain on top and obscure the window I want to look at. That I have to say, is annoying. If I had a bigger monitor, or better yet, dual monitors, I could drag the offending windows off to the second monitor where they will not interfere with other applications.
The default start up mode is "Observe Only" which provides periodic (looks like about once per second) updates to the text values in the Monitor DMM window. Clicking on the View Data button in the Control DMM window brings up another window titled View Data. This window has dialog entries to select how many readings to recover form the 34461A internal memory. For the illustration below I recovered 500 readings.
A nice feature, but the first thing I looked for, and did not find, was a button that would let me export these recovered readings to a CSV file. I'm not sure what the value is in recovering hundreds, or thousands of readings if you can't store them in something like a CSV file.
The DMM Overview button pops up a dialog window that lets the user retrieve several types of non-measurement information from the 34461A including the firmware revision, calibration data, current configuration settings and a couple of helpful tools for learning about SCPI command programming. See the example below:
Every time a generate report request is issued, the results are concatenated to the bottom of the text in the window. For clarity, I cleared the report window for the following two windows.
The two SCPI related report options are interesting to me as I think they will help me understand more about controlling instruments with SCPI commands. The next screen shot shows the result of generating a report using the "Current SCPI Configuration" option.
Again, my small laptop monitor does not allow for the whole list of SCPI commands to be displayed, however, the idea is that this window lists all of the SCPI commands that are necessary to get the DMM into its current state. To see what commands are necessary to change from a current state to another state, you can select "Change in SCPI configuration". So, for example, the meter is currently set up to measure DCV. If I hit the front panel FREQ button to change function to frequency measurement, then generate a report with the Java UI that shows only SCPI commands necessary to change the meter function, the following is returned:
I think this feature could be useful for helping me understand how to use SCPI commands to control an instrument remotely.
Full Control Mode
Now for a look at what is available under full web based control.
Once Full control is selected, the Monitor DMM window allows the user to select a Graphics Display, which retrieves a faithful capture of the 34461A screen image after a second or two delay:
From the Monitor DMM window you can also change the display to trend, bar graph or histogram and obtain a screen capture. The display on the instrument changes to the selected representation and a capture is sent to the computer.
Once full control is enabled, all of the grayed out controls on the Control DMM window become available for use. See the image below to get an idea of the range of control available through he Java UI.
The two remaining remote functions are Store/Recall state and Commands. Store/Recall state offers up the dialog shown below. This functionality looks useful for saving and recalling complex instrument set ups. I have often made use of the save and recall configuration features on other instruments, especially oscilloscopes, to save time when returning to a particular measurement scenario. Having the instrument remember what I did to get it into the exact configuration needed for a tricky measurement is way better than relying on my memory or writing everything down on paper and then losing the paper.
The Commands dialog window lets the user issue individual SCPI commands and see the responses.
Finally, back to the last two buttons on the basic instrument web page, there is a LAN configuration page, shown below, and a context sensitive help feature that brings up help text that is relevant to the current active window. The context sensitive feature was helpful to me as I explored the Java UI.
Overall, I am happy with the LAN based control interface and the available features. I am glad this type of instrument control is available to me for those times when remote control of the meter would be advantageous.
To conclude the remote control portion of this review I will soon report on the Agilent DMM Connectivity Utility that replaces Agilent Intuilink for DMMs and I'll discuss my experiences with the iPhone app for Agilent DMMs.
Cheers,
Mark
November 24, 2013 update
Turns out the Agilent software does not run on Windows Vista. My laptop is running on Windows Vista. Also, I don't own an Android or iPhone device. I am one of the remaining die-hard Blackberry users. So, I have a few software and platform challenges to overcome before I can continue with the remote operation review. My wife has an iPhone, so I'll negotiate a temporary borrow to check out the app. Not sure if I will upgrade Vista to Windows 7 / 8. Might just get a new laptop. This one is six years old and though it still works very well, the HDD is full, the SD slot can't read anything bigger than 32 GB and I'd like an HDMI output.
I have made good use of the 34461A in my three blog entires under Test & Measurement. If you would like to read more about this fine meter, please check out the links below:
That's all for now.
Mark
