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Entry  Mon Aug 28 16:19:53 2017, Kira, Summary, TempCtrl, temp sensor TempSenseFront.jpgTempSenseBack.jpgIMG_20170814_121758~2.jpgIMG_20170821_124429~2.jpg
    Reply  Mon Aug 28 22:30:34 2017, Craig, awade, DailyProgress, TempCtrl, temp sensor TempSenseWithLowPassFront.jpgTempSenseWIthLowPassBack.jpgLowPassSchematic.jpg
Message ID: 1883     Entry time: Mon Aug 28 16:19:53 2017     Reply to this: 1884
Author: Kira 
Type: Summary 
Category: TempCtrl 
Subject: temp sensor 

I built a temperature sensor prototype for the 40m lab, which can be used for the PSL lab as well for temperature stabilization. It consists of an AD586 5V constant voltage output, an AD590 temperature sensor (I initially had 592 but they are very similar), and a LT1012 OP amp, along with a 10K resistor and a few capacitors (see first schematic). It uses the temperature of an object that touches the AD590, which is attached to a long cable, and converts it into a current (1microA/K), which is converted by the OP amp and resistor into a voltage. The AD586 is required because the sensor wants a constant input of 5V to accurately measure temperature. I used a 10K resistor on the OP amp so that the voltage should be around 3V when measuring room temperature. It requires an input of +15V and -15V to the OP amp, 15V to the input of the AD586 (this is shared with the +15V input to the OP amp), and a ground. The +15V (red) and -15V (black) inputs are given to the pins closer to LT1012 and the ground is farther away. The output voltage is read out through a BNC cable and can be converted into a temperature in K by multiplying the value by 100, but it shows a temerature that is about 2K higher than the actual temperature.

In addition, I used capacitors on the OP amp to stabilize the voltage input. I used a 100nF ceramic capacitor placed close to the pins of the OP amp and a 100microF electrolytic capacitor placed father away to achieve this. I have attached the schematic for this as well (second schematic), with 1 being the electrolytic capacitor and 2 being the ceramic capacitor.

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