transducer, resistor question

steptoe · Post by **steptoe** » Fri Oct 04, 2013 11:10 am

OK, I recall tinkering with my ebay special 12V aquarium temp monitor with switching for alarm etc, I connected up two transducers to the one unit and the temp reading went low, did it halve aboce C ?? I don't know or recall.

New question ...what if I hooked the one transducer to two units ..is the readout going to be accurate, halved, doubled or just completely inaccurate expression of current temp at the transducer ??
Super Doug ??

Smokey · Post by **Smokey** » Fri Oct 04, 2013 4:31 pm

Whats a transducer...

I was expecting Urban to describe a gender confused person making fresh lemonade.

In all seriousness Jono, I'd like to help as what you talking about sounds interesting but you have lost me.

Gannon · Post by **Gannon** » Fri Oct 04, 2013 4:54 pm

The term you are looking for is "thermistor" which is a resistor who's resistance varies with temperature, usually inversely (as temperature rises, resistance decreases) and can be classed simply as a sensor.

You can only hook up one sensor per display unit, and one display unit per sensor

If you want one display to show 2 sensors, you will need a DPDT switch to switch between the 2. I cant think of a scenereo where you'd want 2 displays for 1 sensor

Subydoug · Post by **Subydoug** » Fri Oct 04, 2013 7:48 pm

More likely to be a thermocouple wouldnt it? If its just two bits of wire tig'd together its a thermocouple, if its some sort of ceramic or potted end then its a Thermister.

Well steptoe, thermocouples work because of the two different metals that are joined together producing tiny voltages which change as the temp changes. Hooking up two in parallel would skew results and I also think hooking up one thermocouple to two different units wouldnt be the most accurate thing to do either. Given that thermocouples run for under 10 bucks on ebay your far better off running two of them. Thats what Id do.

Oh, and make sure if you extend them to run some nice shielded cable or even some cat6 twisted pair works a treat, and you cant solder to the thermocouple so your best off crimping.

Regards

Doug

steptoe · Post by **steptoe** » Fri Oct 04, 2013 8:39 pm

Despite a Bennie lesson in multi quote, no time to refresh

http://www.google.ch.ina may give better (more appropriate) translation

Smokey wrote:Whats a transducer...

I was expecting Urban to describe a gender confused person making fresh lemonade.

In all seriousness Jono, I'd like to help as what you talking about sounds interesting but you have lost me.

steptoe · Post by **steptoe** » Fri Oct 04, 2013 8:40 pm

Gannon wrote:The term you are looking for is "thermistor" which is a resistor who's resistance varies with temperature, usually inversely (as temperature rises, resistance decreases) and can be classed simply as a sensor.

You can only hook up one sensor per display unit, and one display unit per sensor

If you want one display to show 2 sensors, you will need a DPDT switch to switch between the 2. I cant think of a scenereo where you'd want 2 displays for 1 sensor

I can, one unit already in possesion for alarm temp set, another unit already in possession for fan switching, coz I got early gen that switches only at one set temp, not two

It is the little silver sensor at the end of the 12V aquarium alrm temp gadget featured elsewhere here, from ebay

Gannon · Post by **Gannon** » Sat Oct 05, 2013 7:08 am

It will be a thermistor, thermocouples are generally used where more accuracy is needed or for temperatures over a few hundred degrees. Thermistors are cheaper and easy to use

I wouldnt go connecting 2 units to 1 sensor, as it will likely give an unaccurate reading. If you need 2, simply run 2 sensors and attach them to the same part of the engine

steptoe · Post by **steptoe** » Sat Oct 05, 2013 8:40 am

OK. Will update when I fiddle.

tambox · Post by **tambox** » Sat Oct 05, 2013 12:18 pm

Test it, connect one up see what it reads, connect two up see what it reads.
If it stays the same it may work, just test it over the range.
OR if you know how much it alters the reading, recalibrate your trigger points.

steptoe · Post by **steptoe** » Sat Oct 05, 2013 6:52 pm

Sometimes, laziness does not pay off does it