Which Multiplexer to buy?

[gab819]

Hello,

I am currently trying to build a measurement setup to monitor the performance of solar modules.

I already have a Keithley interfaced with Labview that measure the module over time and record the measurements

What I would like is to be able to measure 4 cells with a multiplexer and only one Keithley, programming that with LabVIEW (every 15 min, the system would measure Module 1 then Module 2 then Module 3 then Module 4 by switching the multiplexer and then measuring with with the Keithley)

I have seen the USB‑6001 Multifunction I/O Device (http://www.ni.com/en-gb/support/model.usb-6001.html) and I was wondering whether it was right for what I want to achive or not. Could anyone help me, please?

Thanks,

Gabriel

[crossrulz]

My first thought was to use a DAQ such as the USB-6001.  The only concern I have is the output voltage of your solar modules.  What voltages are you expecting?  If above 10V, then you either need a conditioning circuit or a multiplexer to use with your DMM.  If really small, then you might want to look at getting a DAQ with better resolution.

[gab819]

Many thanks for your answer!

I am planning to carry on IV sweeps (apply voltage, measure the current, then change the voltage etc..) between -5 and 10V so it should be good. In terns of current it should be about 150 mA maximum, will it be fine in terms of current? (I have tried to look at the specifications but it isn't very clear to me).

[Henrik_Volkers]

How is your setup / strategie ? 

How do you want to switch?

Future use? (Flexebility)

Since you already have a Keithley .. my first look (after defining minimum requirements) would be a Keithley switch box ...

(OK, it's more than 20y ago that I last time used a Keithley switcher, but the specs where exelent, today I use RF-PXI ones from NI ...)

[gab819]

Hello,

I was thinking of the following setup:

4 modules connected to the switch, then the switch connected to the Keithley. A LabVIEW programme would select one channel on the switch then trigger the measurement with the Keithley. after that it would switch to the second module, measure, etc...

In terms of flexibility it would be nice to have the possibility to increase the number of modules in the future..

Also, it may be a stupid question, but I found those relay boards online that are much cheaper:

https://www.rapidonline.com/Devantech-USB-RLY08B-8-Channel-1A-Relay-Board-Controlled-Via-USB-60-5058...

They can also be controlled by LabVIEW (via serial command), so it is probably good enough for what I want to achieve and much cheaper (it is good in terms of current/voltage specificatons). Is there any superiority of the NI USB-6001 or a Keithley switch box compared with a relay board?

Gabriel

[crossrulz]

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@gab819 wrote:

I am planning to carry on IV sweeps (apply voltage, measure the current, then change the voltage etc..)

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In that case, you really need a Source Meter with a multiplexer.

Your other option is a power supply supplying a voltage to all of your devices.  The DAQ can measure the input voltage to your devices.  But you will also want to have current sense resistors for each device that your DAQ can measure the current from (voltage drop across the resistor, I=V/R).  There are special amplifiers you could use to turn the differential voltage drop into a single ended (with a lot of gain) for your DAQ to read.

[gab819]

I already have a Keithley for the Source meter. Do you mean I need a Source Meter with a multiplexer integrated in it?