Introduction
I am continuing my series on insulation testers by looking at some of the options at the lower end of the price scale. On this occasion, it is the PM5203 from Peakmeter. Previous insulation testers reviewed are;
Keysight Insulation Multimeter Failure
Chauvin Arnoux CA6526 Insulation Tester Review
Flir IM75 Insulation Tester Review
Extech MG302 Insulation Tester Review
Di-LOG DL9307 Insulation Tester Review
RS Pro RS-9985 Insulation Tester Review
RS Pro IIT1500 Insulation Tester Review
Uni-T UT505A Insulation Tester Review
Sonel MIC-30 Insulation Tester Review
GMC MetraHit Coil Motor Testing Multimeter Review
Brymen BM877 Insulation Multimeter Review
Hioki IR5048 Insulation Tester Review
Megger MTR105 Rotating Machine Tester Review
Peakmeter are a Chinese company and manufacture an extensive range of electrical and electronic test apparatus. In the UK, their products are generally available from Amazon and to some extent eBay. After that they tend to come from Aliexpress or Bangood. Whilst Peakmeter seem to have a range of insulation testers available, closer inspection shows that it predominantly comes down to two units. The PM5203 for a 1000V insulation tester and the MS5205 for a 2500V insulation tester.
Peakmeter Insulation Tester Range
The unit I have gone for is the PM5203.
Unboxing and Overview
The PM5203 comes with a soft carry case, that contains an instruction manual, the meter, a set of leads with moulded probes and a set of crocodile clips. A shoulder strap is also provided for the carry case.
The meter itself has a removable rubberised boot for protection. The front face of the instrument shows the LCD display, the rotary function selection switch and a number of operating buttons to carry out the test various functions, memory and comparator operations. The meter has a moderate set of capabilities in comparison to other insulation testers reviewed.
The meter has the standard 50V, 100V, 250V, 500V and 1000V insulation test ranges that are electronically selected using one of the buttons on the front. Whilst the insulation test has the additional functionality of timed, DAR and PI tests, it does not have any ramp or variable voltage output functions. AC measurement up to 750V and DC voltage up to 1000V are available on separate functions of the rotary switch, with the meter claiming a CAT IV 600V rating. A combined resistance and continuity function is also available however, the resistance only goes up to 200 Ohms with a 1mA test current. There is no capacitance, diode or temperature function often seen on insulation testers.
Insulation test capability is up to 10 GOhms on the 1000V test range, but quickly drops off to 500 MOhm at 500V and continues to drop of the lower voltage test ranges.
The test leads provided are silicone insulated so have a good flexibility and test out above 200 GOhms at 1000V, so will not affect the insulation test readings.
The probe tips have GS38 compatible caps, but I found these to be very difficult to remove to the extent that I end up damaging the caps by prying them off, as can be seen below.
The style of the caps restricts access to the smaller terminals. For these the cap must be removed. The cap must also be removed to utilise the crocodile clips. These are a good size and will easily attach to 12mm motor studs. However, the arrangement of adding them onto the end of the probes makes for a bulky configuration, that can be restrictive around smaller motor terminals.
| {gallery} PM5203 Probe Connections |
|---|
Crocodile clip arrangement for PM5203 |
Probe with GS38 cap fit into 35mm terminal |
Probe with GS38 cap will not fit into 4mm terminal |
Probe with GS38 cap removed fits into 2.5mm terminal |
Crocodile clip on M8 stud |
Crocodile clip on M12 nut |
The final accessory is a padded case for transporting the meter. The is a good size and provides lost of space for the meter and any extra accessories that could be used with the instrument. Whilst the case has no carry handle, a clip on shoulder strap is also provided.
Paperwork wise, an instruction manual is provided that is quite well written and includes basic diagrams and instrument functionality. Being a relatively simple instrument with low end functionality one can quite quickly learn how the instrument functions by carrying out a few tests.
The meter itself is rectangular in format and is a different style to the majority of other insulation testers on the market. Probably the closest would be the Hioki IR4058 that I reviewed back in March 2020. It is certainly different to the U1461A and MIT420/2 instruments that form my baseline insulation testers for comparison during these reviews.
The display is actually quite nice on the PM5203, with the around three-quarters of width being used to display the numerical value and a curved analogue bar-graph displayed above the digits. The display is crisp and easy to read and also has a good backlight.
Performance Tests
To be honest, I was expecting great things with this aspect of the review, but none the less, I ran the instrument through my standard set of tests for evaluating an insulation tester. Lets start with the main insulation test function, due to the restricted test range, I managed 99 tests through the decade resistance box. Response was very respectable, with a maximum deviation of 1.33% being seen.
The deviation plot below shows a reasonable comparison across the different test voltages, with the highest deviations being seen for the 1000V test range, where much higher resistance values are measured and lead to greater in accuracies by design, as is the case for all 1000V insulation testers.
In comparison to other instruments, the PM5203 falls in the bottom third for the overall average accuracy, sandwiched between the UT505A from Uni-T and the MIC-30 from Sonel.
Open circuit voltages are all within specification and were found to be less than 10% for all ranges, which is better than a lot of insulation testers on the market. It is still no match for either the U1461A or MIT420/2.
Voltage regulation on the 500V test range, as seen above, shows a little more spread over the entire test range than the two base units. It is still a respectable result though and better than a number of the insulation testers already reviewed.
The screenshot above shows the output curve of the PM5203 at 500 V. It shows a fairly fast response with a rise time of 26 ms, there was no noticeable voltage spike before there steady output was seen. The scope recorded a maximum of 566 V.
The short circuit current was consistent over the voltage test range and was a little higher when compared to a lot of the other instruments. This is still well within the tolerance requirements of the IEC 61557-2 standard and a higher short circuit current can be useful when charging highly capacitive test objects such as long cables.
The PM5203 seemed to struggle a little with the 1mA load test. Three out of the five test voltages showed borderline results with the current a little lower than the required 1mA for the specific load. The spread across the test voltage ranges was just over 70uA and whilst it is worse than the two base line units, it is not as bad as some of the units reviewed.
At the end of each insulation test, the meter briefly switches to a discharge mode. The discharge resistance was measured at a little over 5 MegOhm, which is on the high side in comparison to other instruments. There are however, a few instruments that have a higher discharge resistance as seen below.
The battery pack for the PM5203 consists of six AA cells, a fairly common set up of insulation testers. Having a limited set of functions, there aren't many load tests to go through, as seen below. All tests showed less than a 1W load, which is a low set of readings, indicating the potential for good battery life.
Battery monitoring within the PM5203 is a simple affair. There is no battery symbol present all the time, the low battery symbol came on at 7.42V, followed by the tester cutting out at 6.60V.
This is a worse than average performance in comparison to the other instruments tested, with only around 27% of the battery capacity being used before the meter cuts out.
Winding Simulator Tests
The PM5203 has both DAR and PI test capabilities, so is an ideal candidate for testing on the motor winding simulator.
Selection of the test function is not immediately obvious as it is with other instruments as DAR and PI are not directly selectable. To select DAR and PI, the Timer mode must be entered and then the timer set to 1 minute for DAR or 10 minutes for PI. If set for either of the values, the instrument knows to perform the relevant test when started and will display a DAR or PI emblem on the display to let the user know. It was noted that when PI test was selected, the DAR ratio was also recorded, something that a lot of instruments do not do.
When in DAR or PI, the test auxiliary display can be cycled between the actual test voltage and the test duration. Using this function, the interim resistance values can be manually recorded to create a resistance plot over the 10 minute duration. Whilst the end result can be saved to one of the nineteen memory slots, the meter only saves the ratio and final resistance values.
The resistance plot from the PM5203 matched the baseline plots from the U1461A and MIT420/2. The DAR ratio of 1.63 from the PM5203 matches the expectations. The PI ratio at 7.59 was a little below the expected 7.80, due to the slightly higher 1 minute value obtained from the PM5203 in comparison to the other meters. However for the purposes of electrical testing the results obtained from the PM5203 were perfectly acceptable.
As already identified, the resistance / continuity function is limited to a 1mA test current against the preferred 200mA offered by a lot of instruments now. Despite this, the results were very respectable with the worst case result being 2.3% from nominal value. The 2 digit resolution enhances the test and provides a better result than some more expensive instruments reviewed. It would certainly be interesting to get hold of an MS5203A unit that does have the 200mA test current to carry out a comparison.
Motor Tests
I did not take this tester into work to test motors or generator windings with, as it just isn't up to that kind of testing in my opinion. I did however, test it against a small three phase motor to show how it operates for someone who has had issues with their unit, so I will put the video for these tests down below, in case anyone wants to get a better idea of how the PM5203 operates.
As the video explains at the end, I also tested the same motor with the MTR105 that showed good correlation with the results for the winding resistance measurements, with the insulation test results showing slightly lower values using the PM5203 against the MT105.
Build Quality
The PM5203 consists of a hard plastic case, surrounded by a removable rubber boot. Whilst the case seems to be relatively consistent across the many variations of this model of insulation tester, the rubber boot seems to change colour dependent upon the manufacturer. For Peakmeter the boot comes in a high visibility orange. The rubber boot is relatively easy to remove and seems to hold itself in position via several recesses in the plastic case.
At the rear of the meter, the battery compartment can be removed with the rubber boot still on the instrument. The battery compartment lid is held in place by two machine screws at the bottom and plastic clips at the top. Brass inserts for the machine screws can be seen in the case. The foldable stand comes away with the battery compartment lid.
The case is then held together by a Philips screw in each corner. Removal of these allows the instrument case to be split in half to reveal the main circuit board and a smaller, separate board by the input jacks. The lead for the battery compartment can be unplugged and the rear case half moved away, but the leads to the input jack board are hand soldered at both ends.
The smaller input board looks to contain some rectifier diodes and PTC. There is no evidence that I saw of a voltage dropper circuit on this board or any other form of input protection such as gas discharge tubes or varistors. The continuity function does not appear to be fuse protected. The input board is screwed to the plastic case with the input jacks soldered directly onto it. The arrangement does look to be secure.
The vast majority of the components are on the main board screwed into the front half of the case
The four corner screws can be removed and the complete PCB lifted out.
Interestingly, the rotary function switch turns out to be a completely enclosed unit, which is unusual in comparison to other instruments I have looked at. The push buttons are the PCB / carbon pad arrangement commonly seen. There was some evidence of flux residue on this side of the board around the areas that appear to have hand soldered joints. By the side of the rotary switch, the MS5203 designation of the Mastech unit is a clear giveaway of the origins of the PM5203.
With the PM5203 being a relatively basic insulation and continuity tester, there isn't much going on within the case. I have identified the main processor as a M430F437 micro controller from Texas Instruments. The details are readily available for this, which is nice as I have deliberately chosen this unit to do some reverse engineering on to enable me to learn more about the internal functioning of an insulation tester.
Conclusions
This is actually not too bad an offering from Peakmeter at the lower end of the insulation tester market. In comparison to a lot of other instruments, it lacks a lot of functionality, but it is quite sturdy and reasonably well built. Performance is average in comparison to other instruments, which is surprising given the price bracket it is in.
It is a little bit quirky with some of its control and the selection of the DAR and PI functions, but these do work as required. The addition of a timer allows for manual data to be recorded easily. For my work the low insulation reading capability along with the 1mA test current of resistance measurements means it is not really suitable for my needs. It is however ideal for investigating the internal workings of an insulation tester.
If you can pick the unit up at the bottom end of the price range, then it is usable for general electrical work, such as testing cables and white goods. I do not understand the price range that some of the other clones are being offered at, unless there is some significant improvements in their units that I am unable to determine.
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