we use a really elegant little system with a small heating block about 1.5 inches by .5 by .5
( a metal block with i dont know what inside- some sort of resistor that heats up)
- Our perfusate passes along pvc tubing and then into and out of the heater 4 times
and then it immediately enter the bath with the slice. The heater is slung under our perspex
recording chamber and linked to a little 'box' away from the chamber we can monitor the heater
temp or more usefully the bath temp with a small probe in the solution right next to the slice.
The temp if fairly stable - even between summer/ winter mine still is at the same temp.
I have just discovered that they are actually made for us in house, but that the electronics
guy does make and sell them outside the dept. If you contact him next week ( he's on holiday)
he'll give you more details, prices etc
His name is Chris Annetts and his number is 01865 271858.
I hope this info is of some use to you