Products > Test Equipment
EEVBlog 121GW Multimeter Firmware Details
Terry01:
--- Quote from: CDaniel on December 04, 2018, 10:30:18 am ---
--- Quote from: Terry01 on December 04, 2018, 09:31:57 am ---Ah ok, I can do that no probs at all but you'll have to just take my word for the results as I don't have any recording gear to make a decent video of the outcome. :(
--- End quote ---
Terry01 , we don't need proofs , user observations and feeling is enough .
--- End quote ---
I spent 45 mins or so there with my 121GW and U1273a just measuring lots of different things between the two meters. I used 2 sets of the same leads in both meters depending what I was measuring. So the test was as fair as I could make it leads wise.
First off before I say anything when I first got the 121GW with firmware v1.54 installed I tested a load of resistors, caps, diodes and anything else I had laying around and I thought it wasn't that bad.
Today with it side by side with another meter it was awful! Very slow in everything apart from DC volts where it was ok or as good as the U1273a and it also jumps around quite a bit.
When measuring resistance it always jumps to between 20-40k and then settles on a more realistic number where the U1273a just lands on the measure and stays there solid.
On AC volts it's a wee bit slower than the U1273a but settles fine after a couple seconds.
I also measured the A ranges with a couple 9v batteries, 1 has been used a little and 1 is quite quite badly depleted which was very strange.
I used a 3.9 ohm power resistor as a load. Both meters showed around 87mA on the A range when measuring the newer battery but when i then changed range to mA range the 121GW would not read it and kept showing OFL where the U1273a measured it no problems in either A or mA. I found that very strange! The dud battery measured 200-300 uA or there abouts and both meters measured this no problems in the mA range.
When i tested the 121GW on it's own when i first got it it really didn't seem that bad, maybe my inexperience played a part in thinking that too though.
A couple things to sum up... the U1273a is around £100+ more expensive and has had time to iron out all the teething problems etc and also Keysight has much more experience and has made loads of previous other meters to gain knowledge from along the way. I think the 121GW will catch up in time but we'll just have to wait and see. I still use the 121GW at my bench just because i like the meter and a couple seconds extra to wait here and there doesn't matter to me.
I can see where it would matter to someone who needs quick measures dead on every time though. It's funny how a couple seconds extra makes the 121GW seem painfully slow beside the Keysight! :)
CDaniel:
Thx for the honest opinion , can you verify the autorange hysteresis ?
121GW has a huge hysterezis in resistance mode , switch in upper range at 55000 counts and at 40000 counts in lower range , and very big in voltage mode 55000 counts up and 45000 down if I remember correctly .
Terry01:
How do you mean? How would I test that to get the answer your looking for?
Sorry i'm still learning things... :-[
CDaniel:
With a power supply adjust the voltage up and down to see when is switching ranges .
For resistance you need a potentiometer or some kind of variable resistor .
Of course the multimeter must be left connected all the time , not adjust and then measure .
Brumby:
--- Quote from: CDaniel on December 04, 2018, 04:53:04 pm ---With a power supply adjust the voltage up and down to see when is switching ranges .
--- End quote ---
To be clear here:
Step 1: Use an adjustable power supply that can at least go from 3V to 7V. Start at 3V or so and increase the voltage until you see the range change on the meter (watch the units and decimal point). Make a note of the voltage when this happens.
Step 2: Continuing on from Step 1 - From the 7V level, decrease the voltage until you see the range change. Make a note of this voltage.
The difference between these two voltages is the "hysteresis". This is a designed behaviour meant to stop the frequent range changes you would get from a meter without this feature when a measured voltage fluctuates either side of the range switching point.
The issue is the magnitude of this hysteresis. If it's too big then you could have a transient (for example) trigger a switch to a higher range and when the voltage settles it is under that "range up" switching point, but not below the "range down" switching point. As well as being visually distracting, it also means you lose a whole digit of resolution.
This behaviour and the issues associated with it apply to all measurements and ranges - whether voltage, current, resistance or whatever. I just used an easily achievable example for voltage.
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