Post by thread:[OT:] How do you measure hysterisis

I need to measure the amount of hysterisis there is with a pressure sensor and circuit. I have the measuring and pressure applying equipment, I just don't know the procedure and math and stuff. Please assume I am either younger than 9 or older than 40. Thank you John

> I need to measure the amount of hysterisis there is with a pressure > sensor and circuit. I have the measuring and pressure applying > equipment, I just don't know the procedure and math and stuff. > Please assume I am either younger than 9 or older than 40 **. /> Presumably you have either an on /off sensor and wish to measure "stickiness" around trip point OR an analog sensor with electronic output. 1. Digital - Increase pressure slowly - Record pressure where switch activates. - Decrease pressure slowly. - Record pressure where switch deactivates. Hysteresis % is (Pon-Poff) * 200 / (Pon + Poff) % 2. Analog Start at 0 pressure and slowly increase pressure to max and then decrease to zero again. Plot Pressure versus voltage curve. Hysteresis causes the area between the ascending and descending curves. % hysteresis depends on what use you want to make of the data. At any given pressure its (arguably) as above but substitute analog output variable for pressure. eg (Vup - Vdown) * 200 / (Vup + Vdown) % Russell McMahon Aged 42* (base 13) *** * The answer to life, the universe and everything. ** To what base? *** Where the 13 is to base ten.

John Pearson wrote: > I need to measure the amount of hysterisis there is with a pressure sensor and circuit. I have the measuring and pressure applying equipment, I just don't know the procedure and math and stuff. Please assume I am either younger than 9 or older than 40. So that means you are either smart enough to find it on the web in a second, or that you wouldn't remember the answer even if we gave it to you? <G> Step the pressure up to a calibration value, and take your reading. Step the pressure down to the SAME calibration value, and take your 2nd reading. If they are not the same, you have hysterisis. With a dead weight tester this is done by adding 1 then 2nd weight, then removing the 2nd weight. You usually get different hysterisis values for different step sizes. Robert

Russell McMahon wrote: > Hysteresis % is (Pon-Poff) * 200 / (Pon + Poff) % I usually look at hysteresis in absolute values (would be Pon-Poff) rather than in %. In many cases, the difference Pon-Poff doesn't change substantially with Pmean (at least not proportionally), which makes the % value not very valuable. And when giving % values, the question is always "percent of what?". Could be % of the actual (or mean) value as you used, could be % of end of scale. So you have to add this information anyway -- then it's easier (and more informative) to say "hysteresis of x Pa at y Pa" than "x% of hysteresis, relative to y Pa". Gerhard