Strange problem with Keysight U1273A Z low function

[Terry01]

I was reading through the user manual for my 1273A the other day and found that the "Z low" feature can be used to indicate whether a battery is really dead and on it's way out or not.
I use my old batteries for some bread board projects and stuff like that after the have been used in my meters or whatever. The lithium ones seem to last a while even after they are not up to powering meters or whatever anymore. 
My DE-5000 was struggling to test some caps I was playing around with and as the battery was getting down to 1 bar I thought that might be the problem. It was reading 7.8v or 7.6v if I remember correctly. I changed the old battery for a brand new one and the problem was solved. The DE-5000 worked as it should again.
It was displaying in pF when I was measuring uF sized caps for anyone interested. If your DE-5000 exhibits this behaviour. change the batteries out before taking it apart!

Anyways... my U1273 won't measure anything apart from A or mA/uA for about 5-10 mins after testing a 9v battery with the "Z low". It just shows blank spaces where the numbers should be but displays the range and any other info normally displayed on the screen for a given mode. After around 5-10 mins it measures everything fine again like nothing had happened.
Does anyone know why this is or does their Keysight meter do this also?
I don't want to contact Keysight if it is something I am doing wrong although it does say it can perform this in the manual.   

[MosherIV]

Sounds like a firmware bug OR
the lowZ resistor has overheated and affecting the analogue front end circuit.

[Terry01]

Yes, I would agree the same things. It would be interesting to see if anyone else's Keysight meter does the same thing or if it is just my meter.

[rsjsouza]

Terry, I just tested my U1273A and it worked instantaneously. Using a regular power supply, I set it to something relatively low (1.2V current limited to 100mA), measured in Zlow, then immediately measured the current in A, mA and uA. No lag whatsoever.

[Terry01]

Terry, I just tested my U1273A and it worked instantaneously. Using a regular power supply, I set it to something relatively low (1.2V current limited to 100mA), measured in Zlow, then immediately measured the current in A, mA and uA. No lag whatsoever.

Cool, thanks very much for the info! 

A, mA and uA are all fine after using the "Zlow" mode on my meter too, it's all the other functions that act funny.
All the "Volts" functions, diode, capacitance and resistance act funny for 5-10 mins after measuring a 9v battery in "Zlow" mode.

Do you have a 9v PP3 battery you could try, the square shaped battery? That is what was causing my meter to act funny after measuring it in "Zlow" mode.

[rsjsouza]

I tested on both a 9V battery and a 12V VRLA. I left it for 15s before switching functions. All good.

BTW, the Zlow is a high impedance for most batteries - mine reads 1.67k, which is a very small current for 1.5V cells.

[Terry01]

I tested on both a 9V battery and a 12V VRLA. I left it for 15s before switching functions. All good.

BTW, the Zlow is a high impedance for most batteries - mine reads 1.67k, which is a very small current for 1.5V cells.

Cool, thanks again buddy. Maybe a 9v(down to 7.6v) is too much then and it needs the 5-10 mins to settle again before taking measurements?
I'll test mine on a couple AA's and also a couple AAA's too and see what happens. Ill let you know how I get on.
Thanks again for the help, it's much appreciated buddy 

[rsjsouza]

I have the low pass filter disabled (it was enabled by default in one of the firmware iterations) - perhaps this could explain the lag? All other settings are default.

[Terry01]

I have the low pass filter disabled (it was enabled by default in one of the firmware iterations) - perhaps this could explain the lag? All other settings are default.

Ah ok. That is way over my knowledge level. The LPF is enabled on my meter by default when I select to measure just DC v.

I just tried measuring a mixture of AA, AAA and a few different coin cell batteries in Zlow mode. They all measured around 800mV - 1.6V or there abouts. I tried measuring DC v periodically during testing of these batteries. There was maybe 12-15 of them in total and every time I measured just DC v again it worked fine.
I thought this obviously means measuring the 9v batteries in Zlow mode was too much for the meter so problem solved.

I tried measuring a 9v battery again in Zlow mode just to confirm this and the meter worked fine in DC v mode right after making a complete liar of me!
I tried to get the meter to repeat the problem a few times but every time I flicked back to measure DC v it worked fine!    LOL

[rsjsouza]

Gremlins... Gremlins... It's all their fault.

[Terry01]

Gremlins... Gremlins... It's all their fault.

I think you may be correct... either that or I am going a little nuts! 

Thanks again for taking the time to help 

[Terry01]

SooOO.... the gremlins have been in about my meter again...I think! Only this time I was testing a couple of CR2032 button cells. The meter displayed the exact same "no numbers" weird behaviour as it did before. I will send a mail off to Keysight and see what they say.....