Pretty slick! I originally had a pressure switch that would be open below 60 PSI and closed above 60 PSI for monitoring the pneumatic system using a digital input. That is for our fault tree compliance with ASTM guidelines (shut the motion down if we are below that threshold).
At some point I installed a backup electric compressor which is controlled by the computer. If the pressure was below 60 PSI the compressor would turn on – but when do we shut it off? It is a dumb pump with no switch of its own. The computer was instructed to only allow duty cycles of 10 minutes so it would basically run for 10 minutes then shut off and be above 60 PSI.
A solution was a different pressure switch – one that opened on pressure fall below 50 PSI but didn’t close the switch until it got to 90 PSI. Seemed like the perfect solution! However, for ASTM compliance we may comply with 60 PSI but not know until we got to 90 PSI. There had to be a better way!
This guy has a 0.5 V to 4.5 V linear signal voltage representing 0 PSI to 200 PSI respectively. Instead of using a digital input, I put it on one of my available analog inputs and viola! I have a pretty accurate measurement throughout the range of pressures at any time for about $25!