Wiring an E888`s TC inputs

[Martin]

Hi,


Im building an engine harness for a vehicle. The harness includes a Mil-spec Connecor (D38999 type) that will disconnect the part on the engine from the firewall when the engine is removed. My question is about thermocouple wiring. Would it be a problem to Wire the TC+ and TC- inputs from the E888 with 22g tefzel wire, trough the Mil-spec connector (gold plated contacts) to a 2 pin DT series (deutsch) connector and then wire from the 2 pin DT connector to a thermocouple? All the contacts would be gold plated contacts.


Thanks
Martin

[DarrenR]

Hi Martin,

It is fine to wire this way as long as you measure the temperature of the connector to the thermocouples with the cold junction compensation on the e888.

The way the temperature is measured is by the type of wire used, the two wires are made from two special metal that joined at the tip of the thermocouple. The DIFFERENCE in temperature from the 'hot' junction (tip) to the 'cold' junction (connector) actually generates a small voltage from junction to junction. The cold junction being from the thermocouple wire to any other type of metal. The change in temperature of the cold junction affects the temperature reading 1:1.
The e888 has two inputs for cold junction compensation using bosch water temp sensors. If you were to measure the temperature of the TC connectors then this is fine. Otherwise you need to use TC wire and TC pins in the connectors all the way back to the e888 and use the e888 temp as the compensation.

[Martin]

Thanks Darren,


I now understand what CJC is for

[yai111]

If I connect TC with DTM gold connector on the wire end and extend the wire with tefzel wire and input to AMP Superseal on E888. How and where do I put CJC (Bosch 026 sensor)?

[Stephen Dean]

Hi,

The CJC sensor needs to be mounted at the point that the wire type changes, so in this case as close to the DTM connector as is possible.