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Arduino csv coolterm3/8/2023 The backyard patio was my "thermal chamber":)įigure 3 shows my overnight test setup. A better approach of course would be to put the setup in a thermal chamber but I didn't have one handy. txt) and Excel will read it directly into two separate columns. Tip: use a serial terminal software such as "CoolTerm" that allows you to save directly to a text file. Next, I just simply let the program run over a 24 hour cycle and imported the results to a spreadsheet. Notice that these modules take a maximum of about 340 ms to return a measurement, so averaging over many samples can take some time. I actually averaged the results over eight samples to reduce "noise" in the measurements. The software produces a measurement every minute for both Voltage (V measured) and the Sensirion provided temperature (T measured) and displays it in the serial console. To collect my calibration data I used the following Arduino sketch which you can download from the link below. On the software front, I recommend Jonathan Oxer's excellent Arduino library which makes reading temperature and humidity really easy (a simple function call).įigure 2 - SHT15 Module Connected to Prototype Board There are some good web tutorials on how to use these Sensirion sensors with the Arduino. Figure 2 shows how I connected it to an Arduino Nano using only four wires GND, VCC, SCK, SD. Alas, the module is very easy to connect to the Arduino. It's a good "tool" to have in the lab for accurate temperature measurements with Arduino prototypes. The worst-case accuracy is a bit higher than typical (as expected) but still below +/-1 C for the ambient temperature range I'm interested in. This is a very nice module, precise to about +/-0.3 C typical with a 14-bit internal ADC resolution. A sort of reference/calibration tool.Īs luck would have it, the good folks at Embedded Adventures shipped me a very nice Sensirion SHT15 temperature/ humidity sensor module for my projects (Disclosure: I'm not affiliated with Embedded Adventures though they did give me this module for free). However, how do I know what temperature corresponds to a given voltage measurement? For that, we need a precise temperature sensor that one can compare against. (Note: this also assumes the current through the diode and the amplifier circuit is small to where self-heating effects can be neglected). In my application, VOUT is connected to an ADC input in the Arduino Nano, so this is easy to do in software. We can then infer from VOUT what is the actual ambient temperature. So the idea is simple: periodically turn off the AC component to the circuit and take a couple of measurements of VOUT (DC component only). Let's see how this is done in practical terms. Granted, this won't be a precision sensor but the information comes essentially "for free" and can often be useful. Besides measuring whatever it is that you are measuring, you can also get a temperature measurement. This is a technique that I suspect one can apply to many circuits. Can we extract useful temperature information from this DC measurement? As we will see sortly, turns-out we can. The primary use for the circuit is to measure the AC level, but if I turn the AC source off, I can also measure the DC component. What you are left with at the output VOUT is just the VE (Emitter) bias voltage *minus* the voltage drop through the Schottky diode. Now imagine the AC input to the amplifier is turned-off. Normally, there's an AC component riding on the emitter voltage of the transistor amplifier along with a DC bias voltage. This is part of a project I'm currently working on (more on it soon). Take the circuit in Figure 1 for example. Often, these thermal effects are a nuisance, but we can sometimes turn them into useful information. With electronics, most physical quantities vary to some degree with temperature, even if that was not your primary or intended measurement. This is one of my favorite quotes as it relates to circuit design. "Every sensor is a temperature sensor some measure other things as well" This article shows how to calibrate such a temperature sensing circuit using an Arduino and the SHT15 Sensirion temperature/humidity sensor module. For this purpose, a calibration procedure using a precise temperature sensor is recommended. A simple diode or the output of a transistor bias circuit can be used as a rough temperature sensor.
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