Temp Control

[Steven McWhan]

Hi I need to keep a liquid at 66degrees C with only +-1'C, I have a 2kw
heating element and at the moment i am using a strap on tank 'stat but this
is not very accurate at all, any suggestions?

I am in the UK so 240volts is a must and any off the shelf equipment would
be appreciated.

Cheers

Ste.

 

[Grant Erwin]

You are likely using a "bang-bang" temp controller, the kind that
shuts off when the temp reaches a setpoint and kicks back on when
it goes below another setpoint. There are problems with overshoot
on these systems as well as the inevitable hysteresis band (i.e.
the "dead zone" between the setpoints). What you need is a PID
controller. "PID" stands for "proportional integral derivative"
and it essentially chops the power to the heating element a whole
bunch of times and then controls the duty cycle using a sophisticated
algorithm that forces the error towards zero over time. I'm not
sure what you mean by +-1'C (is this plus/minus one degree Celsius?)
but even a cheap PID controller should have no problem with this
switch. 240 should be no problem. Try http://www.omron.com they
have lots of products that can work for you.

Grant Erwin
Kirkland, Washington

 

[John Jardine]

Hi I need to keep a liquid at 66degrees C with only +-1'C, I have a 2kw
heating element and at the moment i am using a strap on tank 'stat but this
is not very accurate at all, any suggestions?

I am in the UK so 240volts is a must and any off the shelf equipment would
be appreciated.

Cheers

Ste.

Farnells do a versatile, 'Carel', digital display, temp' controller part No
645-345 at a surprisingly cheap £43 +Vat.
I use one in an oven for electronics testing and can attest to the stability
of the controlled temperature.
regards
john

 

[Steven McWhan]

Thanks all for your help, farnells have sorted me out.

Regards

Steve.