Help with Edwards Pirani gauge

[Luca Aldridge]

Hi everyone,
I recently tested my vacuum gauge (Edwards Pirani, capable of 1atm to ~10^-3mbar)
It is designed to take a 20-36V DC power and outputs 0-10V DC based on the vacuum (A chart is provided to read it)

With an input of 24V I got an output of 0.2V at atmosphere (should be 10V)
When I turned on the pump with it attached the voltage went down to 0 and when I turned it back off, despite it being sealed and attached the reading went back up to 0.2V
I’m not sure but I expect this is an improper seal, however what confuses me are the readings. It should be 10v to start slowly going down to 5ish (pump rating) but goes from 0.2V to 0V.

Any ideas as to why this is the case?

Thanks in advance!

Luca

[Justin Fozzard]

Hello Luca,
Was that the Edwards gauge that I gave to you for testing your rotary pump?
I had calibrated it on my gauge test stand according to the manual before I handed it to you, so It should be working.
Check that you have wired the connector correctly; it is easy to wire them in the reverse order. A reading below 2V or greater than 10V is an error condition as mentioned in the instruction manual below.

Edwards Active Pirani Gauge Manual.pdf

(922.33 KiB) Downloaded 362 times

Edwards_APG_Active_Pirani_Gauges.pdf

(133.01 KiB) Downloaded 95 times

Next time you visit, we can test it again and I can lend you another if necessary.
I've also had a delivery of several new MKS Series 275 Mini-Convectron gauges that may be of interest to you.

I think yours was the gauge on the right on my Pfeiffer turbovacuum test stand:

Justin Fozzard

[Luca Aldridge]

Hi Justin, Yes it was. I will check and if necessary edit my wiring in the next few days when I have a chance

The wiring diagram says wires 5, 6 and 7 are optional so I didn't wire them, did that play a role or was my wiring just incorrect?

I used an old ethernet cable that fitted the port (connector is the correct one, I'm sure of it) could that impact it?

Luca

[Justin Fozzard]

Hello again,
Pin 5 is the 0V common for the signal outputs, so you should be using this with pin 3 to measure the output voltage.

Here is a diagram from the manual showing the socket pin numbers:

The pin assignment:

Edwards APG Pin Connections.jpg (56 KiB) Viewed 1657 times

The wiring diagram:

Justin Fozzard

[Luca Aldridge]

Justin,
Off the top of my head I thought that it was what I had done, as I said I'll double check when I get the chance
Should it still work without using pins 6, 7 and 8 ?(sorry I did use pin5 as per diagram that was a mistake in typing)
Luca

[Luca Aldridge]

Hi Justin,
I've just double checked the connections and they are correct.
The input voltage is correct polarity and voltage, and is DC as specified.
I still get 0.1-0.2 V readings.

How do you suggest I proceed?

Luca

[Luca Aldridge]

I've got it working, reading 10V at 1ATM. since i have no access to the rotary pump I'll test the gauge on the school's own pump against their gauge to test accuracy at lower pressures.

[emoran]

Hey I am having a similar problem how did you solve this?

Thanks in Advance

[Luca Aldridge]

The mistake I made was reading the wiring diagram back-to-front. Have you tried reversing the order of the wires?