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Example Project: 20 Channel solid state scan card for K2000 DMM

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Had some free time to work on this
I tested a few G3VM-61VY3 SSR to see if there are outliers that I should not use.
Screenshot below is of 3 SSR. (next to each other in the packaging)

Led current was 5mA 1.26V  (yellow)
Voltage over the output (blue)  serie with 2.1 Ohm and 0.5v supply and 0.3 Ohm wire gives about 0.5 Ohm that is above the typical 0.15 Ohm (max. spec: 2 Ohm), probably some other small resistances in the test setup are making it difficult since it's not a soldered setup.
'Vp-' gives an idea about how equal the resistance is. (assuming the setup stays the same)
'vpp' would be the voltage over the resistor.

Timing ON is about 1.4ms edge to edge but to 'ON' you need to add 0.2ms (see screenshot), that is below the typical 2ms.
Trigger OFF is very fast 0.078ms so that's good, below the typical 0.1, so you don't have to wait before enabling the other relays. (in theory you could do it at the same time without creating shorts, having 1ms margin)

With 7.5mA 1.3V Led I get about 1.0+0.2ms on time, off time is the same <0.1ms (there were even a few with 0.90+0.2ms on time.)
7.5mA is also the advised current for this SSR according to the spec sheet.
So for this SSR I will change the 470 Ohm on the PCB to 300 Ohm.

If someone knows what the reason is of this small hiccup near complete open (blue falling edge), feel free to let me know.

1) The hiccup was the power supply who couldn't follow the fast current step. (about 150mA , <1ms)

2) I also did some measurements with 10 Mohm in serie (like Voltage DMM6500, I used the scope probe 10Mohm in serie) with the SSR, Supply 0.5V, then it's faster on:
ON 0.53 ms with 7.5mA led
ON 0.45ms with 10mA led
OFF 0.10 - 0.11ms is typical

17 * G3VM-61VY3,  3 * VOR1142M4T, both 1V 1kOhm load (1mA), 7.5mA led.
yellow is again led voltage, blue is SSR out voltage.
First timing is ON edge time, second timing is OFF edge time.

Anders Petersson:
Thanks for sharing, Kedas
I use G3VM-61VY2 for 4-wire resistance measurements with good result.


I do have a spare PCB but I don't want to go to the trouble of shipping for this price.
Have you tried ordering the PCB? (The price isn't very high, most of the cost is in shipping)
Just upload the provided zip file from the thread starter in https://cart.jlcpcb.com/quote

The pictures I provided are so you would see what you receive.

P.S. 'ghg' Your PM inbox is full.


Has anyone been working on the thermocouple card?

I just use PT100 4W with the standard card.
CJ comp is a bit of a pain because you need an iso-thermal block for the contact block, like the copper one in 2001-TSCAN.


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