Edwards Pirani Gauge/Display Troubles
Posted: Sun Dec 11, 2016 5:18 pm
Hooked up my Edwards RV3 to the chamber last night, along with Pirani sensor and display to see how it performed.
Quickly ran into trouble with my setup though, as the display didn't show any change in pressure, it just sat around its normal atmosphere point. If I gave the display box a firm (light) whack, the needle would swing down from atmosphere to somewhere in the 100 micron range, but would return straight to atm. If I whack the display box with the sensor at atmosphere, there is no swinging of the needle. If I blow into the sensor in open air, the display registers some increase in pressure, swinging beyond the atm mark. The orange light on the display (see picture) flickers a little bit when the sensor is under vacuum, no flickering when the sensor is at atmosphere - I don't know if that 's relevant.
I know there's some level of vacuum being produced by the pump - When I open the KF flanges, there's quite a bit of sucking and whooshing as the chamber comes back up to atmospheric pressure - the problem isn't the pump.
So, the problem seems to be that the readout isn't properly showing what the sensor measures. The reason I don't suspect the sensor as much is that there is some response on the readout to changes in pressure (ie swinging from atm to 10 - 100 micron and back with a tap), so the sensor seems like it's sending back a signal, just the display isn't showing it properly.
I guess my next step would be to confirm the sensor is working. From reading old posts, Chris Bradley described these as 'glorified voltmeters' and advised a voltage across the two appropriate pins on the lead and read the voltage signal output, seeing how it changes with pressure and checking against the calibration curve. http://fusor.net/board/viewtopic.php?f= ... ani#p26491 The connector on the sensor is a weird one - have attached a picture, anybody able to identify it?
Is this the right way to proceed? Would anybody have any goto suggestions for what could be going wrong and how to fix it?
Thanks,
Tom
Quickly ran into trouble with my setup though, as the display didn't show any change in pressure, it just sat around its normal atmosphere point. If I gave the display box a firm (light) whack, the needle would swing down from atmosphere to somewhere in the 100 micron range, but would return straight to atm. If I whack the display box with the sensor at atmosphere, there is no swinging of the needle. If I blow into the sensor in open air, the display registers some increase in pressure, swinging beyond the atm mark. The orange light on the display (see picture) flickers a little bit when the sensor is under vacuum, no flickering when the sensor is at atmosphere - I don't know if that 's relevant.
I know there's some level of vacuum being produced by the pump - When I open the KF flanges, there's quite a bit of sucking and whooshing as the chamber comes back up to atmospheric pressure - the problem isn't the pump.
So, the problem seems to be that the readout isn't properly showing what the sensor measures. The reason I don't suspect the sensor as much is that there is some response on the readout to changes in pressure (ie swinging from atm to 10 - 100 micron and back with a tap), so the sensor seems like it's sending back a signal, just the display isn't showing it properly.
I guess my next step would be to confirm the sensor is working. From reading old posts, Chris Bradley described these as 'glorified voltmeters' and advised a voltage across the two appropriate pins on the lead and read the voltage signal output, seeing how it changes with pressure and checking against the calibration curve. http://fusor.net/board/viewtopic.php?f= ... ani#p26491 The connector on the sensor is a weird one - have attached a picture, anybody able to identify it?
Is this the right way to proceed? Would anybody have any goto suggestions for what could be going wrong and how to fix it?
Thanks,
Tom