Temperature sensor for DAQ board

Hi,

I want to automate my brewing system with thisboard .
I've tried to concet LM35 to one of the 10 bit ADC inputs.
once I pluged the USB the sensor got very hot, and I didn't got reasonable readings.
Not sure why, maybe because the voltage supply from the board is not stable enough for that kind of sensor.

Any ideas which sensor to use and how?

Thanks,
Royi

I've used a MCP9700A from Dallas / Maxim Semiconductor. You can probably get a few sample parts to tinker with if you sign up. It's a similar analog sensor, and I've had good luck with it.

bblack7489 said:

I've used a MCP9700A from Dallas / Maxim Semiconductor. You can probably get a few sample parts to tinker with if you sign up. It's a similar analog sensor, and I've had good luck with it.

Click to expand...

Thank for the reply.

does it need stable voltage?
did you need low pass filter at the input to the ADC?

How unstable is your supply? Any chance you have a scope to look at it?

From the looks of the board, the 5V supply is coming directly from the USB. That should be pretty stable, especially with what appear to be two filtering caps. If you're really worried about it, you might try putting a 0.1uF and 10uF cap across the power pins to smooth it out a little.

As for low pass filtering, I typically do a running average in software using 4 to 6 values. You could probably also over-sample and then compute the average. Typically the temp values are changing so slowly that averaging works really well. If you're worried about that, you could make a passive low-pass filter with a cap and a resistor before you read in the value on your ADC.

I don't have have a scope, just fluke.

by unstable I meant that the voltage is changing depending on the load.

without any load I get 4.8
with the relays board it goes down to 4.6
on the LM35 I measured 1.8V between Vcc and ground (not sure why, it should be the same as the supply voltage to the board)

what bothers me is that without knowing the supply voltage I can't convert the ADC reading to temperature.