Are the meters supposed to come with a pre-installed microSD card?Yes. Sandisk edge 8gb in mine, but don't know if all the same.
I found that when I took my meter apart the range selection knob had a smooth clicky feel to it, but when assembled with the shim it had a rough, grindy feel that I didn't like.
I observed that my meter had the same raised molding artifacts that Scottjd pointed out. So I did two things: I smoothed down the raised projections using fine sandpaper, and I applied a small amount of white lithium grease on the contact surface where the shim rubs against the meter back. Upon reassembly my range selection knob now has a smooth, silky and clicky action that it didn't have before.
Can someone do a test on their 121GW to see if it's the same as mine?
1. Put the meter in resistance mode
2. Manually set the range to 0.000 Ω
3. Short the probes (use alligator clips so you don't have to hold them)
4. Expect to see a fluctuating reading in the 0.03 to 0.05 range depending on the probe resistance
5. Press the min/max button to capture the max reading
6. Now lightly touch the HOLD button with your finger and pull it away again (don't press it, just touch it gently)
What does the display capture?
On my meter the reading jumps up dramatically as high as 0.2, 0.3 or even 0.5 Ω
Something similar happens if I press the REL button to null out the probe resistance. Pressing the REL button makes the reading jump high, making it impossible to null out the probe resistance in this range.
Also, occasionally step 4 will show an anomalous reading, for example yesterday the meter showed about 3 ohms. It persistently showed 3 ohms even after turning the meter off and on again and after sweeping the dial through all the other ranges. The shorted probe resistance reading only went back to normal after I put the meter in DC volts and measured a battery. Then suddenly I got the expected 0.035 ohm probe resistance. I have not figured out what event causes the meter to get into this state.
Yes I'm having this, meter goes way out of spec, 0.5 Ω or more, v1.17. It happens whether max mode is on or not.
6. Now lightly touch the HOLD button with your finger and pull it away again (don't press it, just touch it gently)
How to make the meter show weird readings:
1. Put the meter on the Low Z range
2. Measure the mains voltage (let's say 120.0 V AC)
3. Put the meter on the Resistance range
4. Short the probes
You may observe an anomalous reading of about 3 ohms, slowly declining towards zero.
On other ranges (like DC mV) you may observe anomalous readings too.
It's as if a capacitor is charged up and is taking time to discharge back to zero volts. (Or did something heat up and it's taking time to cool down?)
6. Now lightly touch the HOLD button with your finger and pull it away again (don't press it, just touch it gently)
What does the display capture?
On my meter the reading jumps up dramatically as high as 0.2, 0.3 or even 0.5 Ω
Something similar happens if I press the REL button to null out the probe resistance. Pressing the REL button makes the reading jump high, making it impossible to null out the probe resistance in this range.
How to make the meter show weird readings:
1. Put the meter on the Low Z range
2. Measure the mains voltage (let's say 120.0 V AC)
3. Put the meter on the Resistance range
4. Short the probes
You may observe an anomalous reading of about 3 ohms, slowly declining towards zero.
On other ranges (like DC mV) you may observe anomalous readings too.
It's as if a capacitor is charged up and is taking time to discharge back to zero volts. (Or did something heat up and it's taking time to cool down?)
a little sensitivity on the Rel and Mem buttons
Doing LowZ measurement on mains power you stress the PTC that warms up and so the readings need to settle until the PTC has cooled down to normal temperature again. Until this is done you will get wrong ohms readings.
As tautech already wrote watch Joe's video and you will unterstand why this and what happens.
Doing LowZ measurement on mains power you stress the PTC that warms up and so the readings need to settle until the PTC has cooled down to normal temperature again. Until this is done you will get wrong ohms readings.
I got mine on 17th May in Germany. And I got an email 4 weeks before that it was sent to me.
I've been travelling overseas, but now I am back in the lab earlier this week I finally upgraded my 121GW firmware and installed the shim on the selection knob.
Today I went to measure a 12V DC source and the meter displayed 166V. Then it decided to show OFL, even when measuring a 9V battery!
My initial thought was I had accidentally manually selected a low range, or it was in mV mode, or I stuffed up in alignment of the knob position during reassembly. But the display matched the various selected range positions. I took the meter apart and couldn't see any issue... until I removed the range selection switch... and the below image is what I found
I have not been measuring any mains or other high voltages on the meter. The only thing that comes to mind is that the 12V I was measuring was at the input to a couple of POL DC/DC converters which was at the end of a long cable, and the DC/DC converters only had ceramic caps. The DC/DC converter (my own design using TPS54622) is rated at 5.2V 6A out but was struggling to power a Raspberry Pi & pocket 3G router. Measured with another (Tenma or EEVblog/Brymen) meter I was seeing only about 3.8V instead of the expected 5.2V.
I added a 330uF electrolytic capacitor at the input to each of two the DC/DC converters and it solved the problem, so I guess with the long cable from PSU to the ceramic caps was creating a nasty LC circuit and maybe causing some voltage spikes. The cable was ~3m of 18AWG figure 8 speaker cable to simulate what was on-site, and it did help to clearly identify the equipment issue I was tracking down.
No (obvious) damage to the DC/DC converters, Raspberry Pi, or connected equipment, but apparently the meter didn't like it. Or the meter came to me this way as I've hardly used it apart from measuring low voltages mostly out of my sig gen. I doubt that as I'm sure I would have noticed this measurement issue in previous testing.
It was late when this happened and I haven't done further inspection or tried cleaning the PCB yet.
Any thoughts?
Any thoughts?