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Topic: Food Sensor Probe (Read 161 times) previous topic - next topic

hockeymachine86

Hey, I've very new to arduino and was hoping for some help with wiring.  I am wanting to monitor the temperature of meat with my arduino.  I am planning to use a Maverick ET-73 Meat Probe.  So far I am planning to buy a PCB mount 2.5mm female jack.  It looks like the probe has 2 wires and the female mono jack has 3.  How do I know which ones to wire?  Do I wire one to 5V and one to the ground with a resistor in connected in series with the 5V and then find the voltage difference in the middle and send that voltage difference to an analog pin?

Paul_KD7HB

Hey, I've very new to arduino and was hoping for some help with wiring.  I am wanting to monitor the temperature of meat with my arduino.  I am planning to use a Maverick ET-73 Meat Probe.  So far I am planning to buy a PCB mount 2.5mm female jack.  It looks like the probe has 2 wires and the female mono jack has 3.  How do I know which ones to wire?  Do I wire one to 5V and one to the ground with a resistor in connected in series with the 5V and then find the voltage difference in the middle and send that voltage difference to an analog pin?
Until you find or determine the specifications of the meat probe, everyone, including yourself, will only be guessing.

Did you measure the meat probe with an Ohmmeter and try to determine what it is? It could be a thermister and if so, you need to know it's resistance.

Paul

bigred1212

Yes, just guessing.

That probe plugs into a thermometer unit with a display.  It may be the case that the probe changes resistance based on temperature. Different levels of resistance may be interpreted as different temperatures.  It may be the case you could plug in into a jack on a home made board, read the resistance at different temperatures and use an Arduino to interpret and translate those readings into temperature.  Or it may not be the case.
 

hockeymachine86

Yes, its a Maverick ET-732 temperature probe (thermistor).  I think I figured out the PCB mount stuff, but now onto the next issue.  I understand that I need to utilize a voltage divider to get and use the Steinhart-Hart equation to determine the temperature.  However, I am having trouble understanding what resistor value to use for the voltage divider.  I have seen a lot of people recommend 22kohm.  When i measure the resistance of the probe at room temp, I get ~1Mohm.  Is the 22kohm because that is the approximate resistance value around smoking meat temps (~220F)?

wvmarle

The resistor should be roughly the same value as your probe's resistance at the temperature you care about most, so you have the highest sensitivity at that temperature.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

Paul_KD7HB

Yes, its a Maverick ET-732 temperature probe (thermistor).  I think I figured out the PCB mount stuff, but now onto the next issue.  I understand that I need to utilize a voltage divider to get and use the Steinhart-Hart equation to determine the temperature.  However, I am having trouble understanding what resistor value to use for the voltage divider.  I have seen a lot of people recommend 22kohm.  When i measure the resistance of the probe at room temp, I get ~1Mohm.  Is the 22kohm because that is the approximate resistance value around smoking meat temps (~220F)?
What did you find that told you it was a thermister? I could find nothing to allow that conclusion.

Could it be a silicon diode. Did you reverse the Ohmmeter probes to test the resistance the other polarity?

Paul

hockeymachine86

Yes I tested the polarity; no changes. Also, found the following information about the probes.
The resistor should be roughly the same value as your probe's resistance at the temperature you care about most, so you have the highest sensitivity at that temperature.
Thanks!  That's what I was thinking, but couldnt find it written down anywhere.  I think this site tries to help with that resistor selection.

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