I have a thermostat that is cleverer than me. If the hysteresis is set for 1 degree and the set point for 22 deg will the temperature range between 21 and 23 deg or 21.5 and 22.5 deg. My question relates to the actual temperature reading which remains in 21 deg.

My guess is 21.5 to 22.5. Hysterisis is measured from on to off

Cheers

Go digital - no problem then

I have gone digital and that is the problem. Set point 22, histeresis 1, lowest temp 20, highest temp 24 and actual temp 21. Read the instructions (a problem for us guys it seems) Cuts in less than set point and out at set point. Made in USA with instructions from Mongolia. I may have been dropped on my head as a baby but I would have thought that if you set it at 22 that is what you would get, not 21. However it works, it just helps to have Irish ancestry.

I see no problem at all if that's what it's designed to do. Don't complain if the temperature doesn't stay at the point you have it set to turn off at long. You're not setting the temperature it will hold. You're setting the point it turns the heater off.

As I said, it is working well, it has just been a challenge for someone as electronically iliterate as myself. The problem is not the gadget but the brain cells trying to control it. It is true--- if all else fails "read the instructions"

Strange. Hysteresis is a bad thing in control systems. Do you have a setting (ie. can be twiddled with) for hysteresis?

I would interpret an hysteresis of 1 degree as meaning it will overshoot by 1 degree. that may be ok for use in a fish tank, but it's not a very well designed heater given that you have the thermal mass of the tank to damp out any feedback loops.

Digital in, digital out: "going digital" is going to be the downfall of Western civilisation. A heater is analogue (at least to any useful degree unless you happen to be a quantum physicist). All "digital" means is that they are too cheap to put a decent control system on it.

It can be adjusted but it is set at the minimum of 1 deg.