Temperature differential switch

From: Bret Pehrson (bret_at_infowest.com)
Date: 06/11/04 

Date: Thu, 10 Jun 2004 21:42:27 -0700

I need a switch based on (variable) positive temperature differential between
two sensors (thermocouples).

By positive temperature differential, I mean that if one thermo reads 50 and
the other 65 (presuming a 10 degree on setting for the differential), the
switch would be on, but if the same thermos read 50 and 35, the switch would be
off.

Specs:

  Input: 120 VAC
  Switch: 120 VAC 3 A
  Differential range: 0-50 degrees F
  Accuracy: 10%

May be electronic or mechanical, no low-voltage power supply, unless on-board
and minimal components. Entire component (excluding leads for thermocouples)
must fit in 2"x2"x1" or there abouts

Anyone interested in taking on the project? I am willing to pay for design and
prototype if it can be designed to the requirements.

Relevant Pages

  • Re: hayward pool heater millivolt 350 type
    ... Thermocouples put out around 25mv. ... You can jump the pressure switch momentarily and if the heater fires, ... Either the filter needs backwashing or a bad switch. ...
    (alt.home.repair)
  • Re: Fridges
    ... The technology uses large thermocouples one set cooling the interior and a matched set throwing out heat outside. ... We had one or two unfortunate incidents until I fixed a bit of Perspex across the switch to stop it being accidentally switched. ...
    (uk.rec.waterways)
  • Re: Switching thermocouples
    ... Temperatures involved lie in the range 10-45 ... run both thermocouples to a change over toggle switch and then on to ... throw switch, if there is no conductive path between them then a single pole ... chromel or alumel junctions that you create at about the same temperature. ...
    (uk.rec.models.engineering)
  • Re: Temperature differential switch
    ... > two sensors (thermocouples). ... > and minimal components. ...
    (sci.electronics.design)
  • Re: Flourescent lamp -Wasting Power?
    ... > to the real power being dissipated by that electronic ballast. ... > kludge up a setup to measure the real power - without frying myself. ... > stupid design that I just multiplied current times voltage in my head ... > controlled by a single pole four position rotary switch which sequences ...
    (sci.electronics.design)