T4D31 - UT61E

[Kiriakos GR]

And again, nothing you've said has any relevance to my comment. Well done.

Next time make one more well targeted comment.

[bitwelder]

After watching Martin accessing some special modes with powering the UT71D while pressing some buttons, I tried the same on the UT61E. I did not discover much, except two cases:
- if the meter is powered up while pressing HOLD, it keeps the display fully in test phase (all symbols shown) until the button is released
- if the meter is powered up while pressing RANGE button, it beeps twice instead of once as usual. At a quick look I haven't been able to find any difference in behaviour. Does anybody knows more about it?

[dr_p]

You've disabled Auto Power Off

[iloveelectronics]

You've disabled Auto Power Off

The 61E has no auto power off to begin with

[dr_p]

Actually it does, but it's always OFF because RS232 is permanently ON.

ES51922 has a default auto power off function. [...]The APO symbol on the LCD panel indicates whether the auto power off is enabled or not. In some cases, user might want to disable Auto power off. There
are two ways to disable this feature as following:
1. Power on the meter when any of the push functions, except for HOLD is pressed
down.
2. In addition, when RS232 output is active, the auto power off function is also
disabled.

[iloveelectronics]

Actually it does, but it's always OFF because RS232 is permanently ON.

Yes, I meant out of the box it doesn't have that feature so there's nothing to disable until you hack it.

[bitwelder]

ES51922 has a default auto power off function. [...]The APO symbol on the LCD panel indicates whether the auto power off is enabled or not. In some cases, user might want to disable Auto power off. There
are two ways to disable this feature as following:
1. Power on the meter when any of the push functions, except for HOLD is pressed
down.

Hmm... if the manual says that pressing any key except HOLD would disable the (already disabled) APO, why the meter beeps twice only while pressing RANGE during power on?

[dr_p]

it's from ES51922's datasheet. Other than that...i don't know.

[TimothyS]

Hi All,
In the http://www.youtube.com/watch?v=5YbbbgbJK9I (time 4:10) Martin finds an overshoot both at the meter readout, and (worse) the logged PC data.
I noticed that the meter was operated in Auto-Range Mode during this part of the video. Does anyone know if the overshoot also occurs when set to Manual Range? I have a UT61D, and in that unit I can not notice any overshoot of this kind. 

[Rick Law]

Hi All,
In the http://www.youtube.com/watch?v=5YbbbgbJK9I (time 4:10) Martin finds an overshoot both at the meter readout, and (worse) the logged PC data.
I noticed that the meter was operated in Auto-Range Mode during this part of the video. Does anyone know if the overshoot also occurs when set to Manual Range? I have a UT61D, and in that unit I can not notice any overshoot of this kind.

Timothy,

I was guessing it would be the auto-range also, so I did a test on mine.  With my limited resource, I can only go between 3.x volts to + 25.x volts.  That means a single range change between from 22V range to 220V range.

I can see the DMM overshoot to over 120v when it goes from below 22v to above 22v when auto-range kicks in.  It happens frequently.

I tried many times (50-ish), I was not able to get any overshoot when I put the meter in manual - not to say that it wont occur, but I just cannot get it to overshoot when it is on manual range. 

To force a rapid voltage increase, I use a wire to short the trim pot instead of turning the adjustment.  So the voltage goes from 3.x to 25.x as fast as my power supply can manage (< 1 second).  Still, I cannot get an over shoot when on manual range whereas I can cause it to overshoot on auto-range even if I turn the adjustment slowly.

I have a hard time testing the <2.2v switch to >2.2v.  I use power-up of the power supply with a target voltage of 12.x to force it to cross the 2.2v boundary.  The speed of voltage is controlled by how fast the power supply reaches certain voltage so I don't have the option of doing it slow vs fast.  The overshoot from a setting of 12.x volt is not pronounced - at 16v occasionally.  My power supply is capable of doing 16v.  So, in theory, it could be my power supply overshooting the 12.x volt I set it at.  If that is the case (very unlikely), it could be only the range change from 22v to 220v overshoots and the other range change does not overshoot.  Unlikely, but still a possibility.  I just don't have the equipment to test that.

Hope this info is helpful.

Rick

[Rick Law]

Timothy,

... I have a hard time testing the <2.2v switch to >2.2v....  ...I don't have the option of doing it slow vs fast....I just don't have the equipment to test that...

Rick

After writing that post, it just bug me.  I do have something to test it with, I have been too lazy to de-solder a working power board from another piece of equipment that is in service.  It bugged me some much, so I did...

I tested rapid change from below 2.2 to above 2.2v to force auto-range change from 2.2v to 22v.   I set the target at about near zero and rapid increase it to 3.x volt.

Yeah, I can get it to overshoot at the auto-range change from 2.2v to 22v just as easily as I did before when I tested auto-range change from 22v to 220v with my other power supply.  The overshoot is not as pronounced - it overshoot 3.x volt to read as 24.x volt - that board is not capable of producing over 9 volt.  So it has to be a DMM overshoot.  I knew most likely this is the case, but testing with my other board that is capable of producing nearly 40v, it is  possible that the 16v reading was a power-supply overshoot.  Now I know.  Now WE know.

Now I have to solder this power board back in...  I was too lazy to remove that board to test because I know it is hard to put it back - like playing Ma Jong (or Contract Bridge) inside the original mini cooper, you really have to want to do it. 

So, in summary, the verdict is, I cannot get it to overshoot on manual range 2.2v or 22v.  But if I set it to auto-range, it overshoots when it crosses the 2.2v and when it cross the 22v.

Rick

[SeanB]

It looks like the overshoot is a problem in that it updates the display with an incorrect value when it does a range switch, probably because it does a conversion before all the internal nodes have had time to charge to the correct voltages after the internal switching has occurred, but the display drive is configured to show at the higher range. This is an artefact of a high display update rate more than anything else. Thus you find the displayed voltage is somewhere internally between full scale and bottom of scale and dropping rapidly, but is sampled and converted. A simple software fix in the meter firmware would be to blank the display for the first 1 or 2 sample intervals after an autorange event and discard the reading from showing up on the data port, which will not be an issue on a 5 sample a second meter, but will be very annoying on one with a slow update rate.