Author Topic: Multi-channel Voltage & Current Measurement test setup advice?  (Read 472 times)

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Online danielbriggsTopic starter

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Hi there EEVBlog Hive-Mind,
I'm after a bit of advice on the most sensible way to do the following and would appreciate anyone's input / advice.  :)

In short:
I would like to measure the voltage and current, accurately, of at least 3, potentially up to 5 laser diodes simultaneously.


In long:
I have a proper way of controlling and measuring one diode during initial testing + design, using one of these:
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=4053


But would like a way of getting the current and voltage of a bunch of laser diodes while they are hooked up to a suitable driver as a kind of "servicing / production tool". [They are already connected up to a suitable current source, but the drivers have no kind of current read back facility].

The current range through the laser diodes would be in the range of either: 0-0.5A or 0-2.0A (depending on diode type) and forward voltage would be between 2.5-7.5V for all types.
Would like to measure with at least 1mA resolution across entire range, and 10mV for any forward voltage.
I've found the burden voltage of my U1251B or Keithley 2010 is too high to put inline with the diodes for accurate current measurements, so would appreciate some advice on how to best measure this accurately. Hall effect sensor? Are they accurate for <1A at 1mA resolution + accuracy though?
I've read some bits about external current shunts, but have no idea how best to select one over another, let alone their suitability for "multi-channel measurements".

To scale this up to simultaneously measuring 3-5 diodes for both voltage and current, do I use a whole bunch of DMM's with a lower burden voltage? [Dave's 121GW's looked a good choice at 0.03V/A]

Or do I use some kind of multi-channel DAQ that measures voltage only, and use 3-5 µCurrent's to sense the current and convert to a voltage output?
If I go down the "multi-voltage" measurement route, I looked at adding the option of a 2000-SCAN scanner card to the 2010 7.5 digit meter, if that's a cheap and sensible way to do this?

If anyone has any pointers on both:
A. the simple case of accurately measuring current reliably when a laser diode is connected.
and
B. how to scale this voltage+current measurement up for multiple channels (3-5 of each voltage and current) in a kind of basic "servicing / test setup" without spending a million pounds.

Thanks in advance.
All the best,
Dan

« Last Edit: August 11, 2019, 05:32:01 pm by danielbriggs »
 


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