Temperature Sensor on Motor Spindle

[really24]

I need a second opinion...
Philips Semiconductor makes a temperature sensor KTY84-1. I have the spec sheet if you want me to email it.

It basically changes it's resistance as the temperature of the environment changes. It calls for a continuous 2ma currnent. So my question is what is a good way to source a constant 2mA with a 10V power supply?

The sensor basically acts as a variable resistor. I will use an analog input to detect the voltage drop. So on one end I will hook to a 10V source with a continuous 2mA and on the other end I will hook up to my analog input to detect the voltage change.

What do you think? Any opinions?

 

[Paulusgnome]

A thermistor sensor such as this is feasible. What you need is a constant-current source - this is a fairly standard sort of circuit that you should be able to find in any analog electronics textbook.

A much easier way of doing temperature sensing is to use an LM35 precision temperature sensor. These are cheap, easily obtained and are manufactured by several companies. They do not require much support circuitry, tolerate wide supply voltage variations without degraded performance, and produce a precision voltage output of 10mV/deg C which is easily scaled with an op-amp or two if 0-5V or 0-10V signal is required, say for a PLC input.

 

[really24]

Thanks Paulusgnome,
The problem is that the sensor is chosen by the motor manufacturer and is inside the enclosure. I know that you can create a current source using two basic bjt's, but I'd like to avoid making a circuit to save time. I'd like to buy something that could source the constant current.

Would you know of any type product or IC. I have 9 of these sensors to monitor.

Thanks for your reply and help

 

[ScottyUK]

Depending on how 'constant' you want your constant current to be - I guess if you are using a thermistor this isn't a high precision application - you could use a constant current diode.



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