Hi and thanks for the responses,
Reason for the questions. I have just completed a temperature control circuit that utilises a thermistor to control the element in my absorption fridge. The exisitng thermostat has a hysteresis of ± 7,5°C which is unacceptable for me.
Today I was going to send out the artwork to get the boards made (one for me and one for a friend). The new circuit circuit allows one to set the minimum temperature required, the temperature will then drift upwards (the degree to which is determined by the hysteresis pot) and will switch on until the lower limit is reached. I can get about ± 0.1°C which is more than I require, mine is set to 3°C with a tolerance of +1.0 -0.0
I know I don't need it but this is part of learning. From the posts I am led to believe that using PWM on the element it will give me an infinitely more control?
So with my exisiting existing arrangement when the controller see 4°C it switches on and the element will reach maximum sheath temperature and hold it for the duration until 3° is reached when it will switch off.
Would I then be correct in stating that with PWM that the element will probably never reach it maximum sheath temperature. Depending on the setting, the element will be cycling more frequently giving to my mind that is, a more constant but lower heat. This should extend the life of the element as the thermal shocks are significantly reduced?
So rather than sending the output from my circut to control a relay coil I could send it to a PWM controller for nth degree control?
Cheers
Andrew