Group Actions
Engagement
  • Author Author: Jan Cumps
  • Date Created: Date Created
  • Views 2841 views
  • Likes 9 likes
  • Comments 6 comments
Related
Recommended

Keithley DMM6500: App to Hold Measurements

Jan Cumps

I'm road testing the  Keithley Bench Digital Multimeter DMM6500.

In this post, I review an experimental app to implement Hold functionality.

image

The script is made by a Keithley engineer in his free time.

Experimental. See the end of this post for stability remarks.

 

The DMM6500 doesn't have a hold function out of the box.

The App that I'm reviewing here implements it. It shows a maximum of 8 stable measurements.

You can move the meter probes around on your circuit.

Every time it detects a stable measurement, it pushes a new value to the table.

The table is first-in first-out. The 9th stable value will push the first measurement off screen.

Pressing Delete clears all 8 values.

 

Settings

 

The hold app works with several meter functions. The ones not supported are capacity, diode, continuity, temperature and digitising.

You can set a threshold. Any value between that threshold (pos or neg) and 0 are ignored.

The hold tolerance defines in what range measures are considered to be stable. The meter takes 5 measures and if all of them are in this range, it's a stable measurement.

The repeat tolerance defines that any next stable measurement differing less than the % from the previous one is ignored.

If you switch the beeper on, the meter will beep briefly every time a value is added to the hold table.

 

image

 

Changes

 

The script puts the meter in high-z for the DC voltage mode.

This setting is ok when your probes are connected to the circuit, but too sensitive when you are moving from point to point.

The voltage measured in high-z,  with the probes in free air, can easily be more than 7 V.

I changed the input impedance to 10 MOhm in the script.

 

        if     func == dmm.FUNC_DC_VOLTAGE      then dmm.measure.nplc = 2; dmm.measure.linesync = dmm.ON; dmm.measure.inputimpedance = dmm.IMPEDANCE_10M

 

I'd also like to add functionality that, when the value drops below the threshold, the mechanism is reset and the next value is considered as a hold, even if within the Repeat Tolerance.

I gave it a try but haven't succeeded yet.

 

Note: as explained by the author, the example isn't stable at the moment - made in his free time.

That's impressive use of free time, showing a really useful example of an App on the meter.

The instability is real though. I had the meter being unresponsive to the Settings and Delete buttons, lock up when using the app.
It also caused my first blue crash screen - I have firmware 1.0.3c.

The author advices to reboot the meter when you're done uing the App.

 

 

Related Blog
Keithley Bench Digital Multimeter - Review
Software Control Options Pt 1 - TSP Script Builder, LabVIEW, Web Interface
TSP Script Example - Measure Power
How to Create a Bitmap for a Custom App
Verify a µCurrent Manually
Verify a µCurrent in an Automated Setup
Measure Amp-Hours of a microcontroller with a µCurrent
Trigger from External Trigger Input
Trigger from External Trigger Input in LabVIEW
Software Control Options Pt 2 - Test Commands with Communicator
App to Hold Measurements

Store Multiple Measurements Manually

Script Example - Externally Triggered Measurements
  • in reply to aspork42

    James,

      wrote:

     

    ... how does it really work in practice? I (think) I like that it ignores measurements of zero, so it doesn't record every time you pull the probes off to move to a new measurement point... UNLESS recording zero would be beneficial...

    The script holds each stable measurement above - or, if negative, below - the threshold, but only if it is different enough from the previous stable measurement (the previous hold value).

    I haven't tested what happens if you set that threshold to 0.

  • Hi Jan ,

    That's very helpful! Thanks.

    This is what I mentioned last few days about testing and review as well.

    Thanks also for your link to your blogs I've read a bit.

    Yes, that's it - high quality of an report.

    I've bookmarked your blog because this is what we need, helpful information in details.

    As well the manufacturers can do something with this information.

     

    Best Regards

    Gerald

    ---

  • That is cool - how does it really work in practice? I (think) I like that it ignores measurements of zero, so it doesn't record every time you pull the probes off to move to a new measurement point... UNLESS recording zero would be beneficial...

  • in reply to shabaz

    Containerised is key in multi-user. For this single user device I can live with the fact that the standard set is stable and they offer experimental options (quite excited about what the apps will let you do). I’d guess that crash-safe extensions would require some kind of virtualisation in the OS and resource demand is high for that

     

    Kudos to Keithley for being an innovator here. I guess they don’t know themselves at the moment what’s possible with apps. It’s different than scripts, where you automate the instrument.

     

    Here you can convert it to something streamlined for what you need.

    Not needed if what you need is make measurements on a circuit. But I can imagine setups where you can convert it into an application specific device when needed. And turn it back into a normal meter  at will.

     

    This Probe Hold example is the first compelling extension I came accross (the standard example is an on-display analog clock. I find it a little silly, as if they are ridiculing their own invention - like inventing a rocket then shooting the teletubbies to the moon). They also have one to show all measurements of the multi-channel extension card on a single screen. That one I can’t test because I don’t have that extension card. But I think that’s a really useful example too.

  • Not a criticism of the approach they took, since they are opening up tremendous opportunities with the API (and maybe both users and the Tektronix engineers are each still learning its full potential and real-world uses in a multimeter), but I hope their next-generation goes fully containerised apps, so that if they crash, they are isolated. It's already an extremely nice product from what I can see so far.