Posts Tagged pressure switch deadband
Posted by danstips in Air Bubbler, Communications, Configuration, HART, Honeywell, Installation, Level, Level Technology, Paperless Recorders, Pressure, Pressure Switches, pressure switches, Pressure Transmitters, Siemens, Software, Switches, Transmitters, Trendview X-Series Paperless Recorders, Troubleshooting, United Electric on February 2, 2012
Yesterday and today, people all over Chicago and the Midwest were looking at pictures from last year. We had 22″ of snowfall in one day. The roads were closed. The airports were closed. Even the Lesman offices were closed. And today’s weather forecast? 45°… in Chicago… in February.
This morning in Pennsylvania, a groundhog named Phil came out, looked back, and saw… his shadow.
All this looking back made me a little reflective myself. I’ve been writing this blog for about 6 months now. So I thought I’d take a minute and recap the articles people keep coming back to read:
Pressure switch deadband isn’t an unknown, but neither is it a known value when you take a new switch out of its shipping box.
Experienced users will tell you that three identical units of the same pressure switch can have three different deadbands. All three switches will trip at the same pressure setpoint, but reset at different points. To complicate matters, the deadband reset point changes with the pressure setpoint. And, they’ll also say, there’s no way to know, out of the box, what the deadband is without applying pressure and checking.
Who cares about deadband? Not everyone. The exact deadband reset point is critical in some applications, and inconsequential in others.
Why is getting a known, repeatable deadband such a challenge with conventional electromechanical pressure switches, and is there anything to be done about it?