Easy Way To Calibrate a Bryman BM869s Multimeter
After replacing my lost Fluke 87V multimeter with a new Brymen BM869s (rebranded Greenlee in the US) about a year ago, I’ve been delighted with the multimeter. It has every possible function I could ask for and then some. It’s been my go-to meter when working on electronics projects. I do have a Siglent SDM3055 DMM that is very good, but due to its startup time, I usually reach for my Brymen BM869s when I need to measure something, and it has higher resolution. But after getting a broken HP/Agilent 34401A DMM from eBay, fixing it up and replacing all the capacitors, I now have a better reference. I’ve compared it to my friend’s calibrated 6 ½-digit multimeter, and it’s still within spec, so naturally, I want my Brymen to be as close to my HP 34401A as possible. Turns out that calibrating and adjusting the Brymen is quite easy. Here’s how to do it.
Deciding on what to calibrate
I’m only interested in changing the calibration of the DC voltage, especially the 0-50 Volt range. I seldom do anything high voltage, so that’s what I want to be adjusted. Usually, when you do a calibration, you need to go through all the calibration steps, requiring something like a Fluke 5502A, but with the Brymen you can do the first couple of calibration steps and still retain the settings. The DC steps are 0, 5, 50, 500 and 1000 Volts. I can quickly do a calibration up to 50 Volts, but I don’t have the resources or the need for the 500 and 1000 Volts.
Getting the Brymen Multimeter in Calibration Mode
But first, it’s time to start planning on getting your 5 and 50 Volt reference to feed the multimeter during calibration.
5 Volt Reference
First, I needed a clean 5 Volt signal. I have a Siglent SDG2042X Arbitrary Waveform Function-Generator at hand (naturally hacked to 120MHz). The DAC on that unit is 16-bit, and the output has quite low noise. So I put the function generator into DC mode and dialed it up to a bit over 5 Volts. Because I needed to get 5 Volts down to 6 ½ digit precision, I connected a multi-turn 50 kΩ potentiometer that was lying around as a voltage divider to be able to set the correct voltage.
50 Volt Reference
My bench power supply, the Rigol DP832 Programmable DC Power Supply, can only put out 30 Volts on two of the outputs and 5 Volts on the third. Luckily, the power supply outputs are floating, so all I had to do was to connect + from one of the outputs to the – on the other. After enabling “Track On”, I just had to set output 1 and 2 to 25 Volts and get 50 Volts on the two remaining terminals. Again, I used the potentiometer to make fine adjustments.
Time To Calibrate My Brymen BM869s
The calibration procedure is the same for a lot of Brymen and Greenlee multimeters.
- First, turn the multimeter off
- While holding down Select and Hold buttons, turn the selector dial to Ω within a second. If everything worked, you should get 250,000 Ω on your multimeter display. If not, turn off and try again. It’s slightly fiddly to both press two buttons and rotate the dial.
- After you get the 250,000 Ω on display, rotate the selector dial to the part you want to calibrate, in my case, DC Volts.
- When calibrating DC voltage, the first one is 0 Volts. Just connect a short banana test lead between the COM and VOLT socket to short out the input to give you 0 Volts.
- On the BM869s, press the Range and Δ buttons simultaneously to get the multimeter ready. On other models, you need to push Range and the Hz buttons.
- Press the Range and Hold buttons to store the value.
- The display now shows 5.0000 V on the display. Connect the 5 Volt reference, while at the same time measuring with a good meter, and adjust the potentiometer to get to 5.00000 Volts.
- On the BM869s, press the Range and Δ buttons simultaneously to get ready, or Range and the Hz buttons.
- Press the Range and Hold buttons at the same time to store the value.
- The display now displays 50,000 V. Connect the power supply to the potentiometer, adjust the voltage to exactly 50 Volts.
- On the BM869s, press the Range and Δ buttons simultaneously to get ready, or press Range and the Hz buttons on other models.
- Press Range and Hold to store the calibration value for 50 Volts.
- If you have 500 Volts available, you can continue with the calibration, repeating the above procedure. Otherwise, you can just turn off the meter. The stored values for 5 and 50 Volts remains.
Time To Test Your Multimeter
Do a sanity check and compare your freshly calibrated meter with your reference meter. Voilà! You now have a calibrated meter!
If the meter doesn’t show the correct values, do the calibration steps above again and test. Maybe you’re like me, where the OCD goes on full alert if they don’t match!