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The TC-08’s USB connectivity allows up to 20 TC-08 USB data acquisition modules to be used simultaneously on one PC making the TC-08 ideal for use as a large multi-channel temperature acquisition system with a cost per channel significantly lower than other systems of this size. The low conversion time of the TC-08 means up to 10 temperature measurements can be taken every second, while the high (20 bit) resolution ensures that the TC-08 can detect minute changes in temperature. With the TC-08 thermocouple data acquisition module your measurements can be made both fast and accurately. Simply plug the TC-08 into a USB port on your computer, connect your thermocouples, and you are ready to measure temperatures.
You can now connect the logger to the Pi and remove the keyboard, mouse and video to make an inexpensive stand-alone logger storing its captured data locally on a Pi SD-CARDIt is also possible to set an alarm when a device becomes disconnected:an alarm is turned on, the event recorded and the graph annotated to show that the lost data was due to device disconnection. First of all, the answer on a postcard is - if you are trying to do what I think you are, then it can be done with a better NTC thermistor alongside your 10K NTC thermistor, and the TC-08. However, the accuracy of the high precision, high accuracy thermistor you select (which, for example, can be something like ±0.2°C at 42°C) is going to be better than the accuracy of the TC-08 data logger (±0.584 °C at 42°C). The accuracy of the TC-08 is specified with an uncertainty (±) that is based upon factors such as the variation of component tolerances between individual units, and the variation of results between different data capture sessions. You can reduce the uncertainties due to tolerances by performing a calibration for accuracy (which performs measurements of temperature using one channel and one specific sensor to characterize the accuracy of the specific pair over a temperature range). This gives a much tighter uncertainty for the specific TC-08 model and specific channel + sensor, but only as long as they are always used together. The calibration house may then also be able to specify corrections required to reduce even further the extremes of temperature variation over the range. This can be done by making use of the extra resolution available to the data logger to make the corrections with a scaling file. At Pico Technology, we can do the calibration for accuracy for thermocouples, but you would need to approach an independent Calibration House if you want it done for a TC-08 + high precision, high accuracy thermistor.
The Early Access version can also be installed alongside the stable version on Windows and Mac, and will receive independant update notifications for all of the new features added with each release. If users wish to install the last release of PicoScope 6 Beta for Mac (6.14.62), you can do so here. Release notes Picoscope 7.1.17 Early Access Alternatively, the resolution of the TC-08 is considerably better than the accuracy of a high precision, high accuracy thermistor. So, if you are in fact just looking for high precision changes then you already have that capability in your TC-08, and probably don't need to concern yourself with accuracy, calibration, and multiple capture sessions. Note that when discussing how close the measurement is to the True value (qualitative assessment) we use the term 'Accuracy', but when referring to actual numerical values (quantitative assessment) we are actually defining how far away the measurement is to the True value, so the correct term is 'Accuracy Error', which over time has been (confusingly) abbreviated to 'Accuracy'. So, although the thermistor is far too inaccurate and unstable, the TC-08 is a data logger (specialised for working with thermocouples, because of it's CJC, input range, etc, but still a data logger) with differential inputs, reasonable accuracy, and over 16-bits of resolutio, so it is capable of measuring voltage, resistance and current, to reasonable precision. You can measure the resistance of the 10K NTC thermocouple by using a constant current source to generate a voltage across the thermistor. The voltage should be matched at the maximum of your measurement range with the full-scale input for the input range you would be using on the TC-08 Terminal board (so you may need to divide down the voltage using a resistor divider). Alternatively you could use the 4-20mA input range on the Terminal board, and a voltage source, set to a voltage that provides 20mA through the thermistor at the maximum temperature of your measurement range.In considering your measurement goals it's worth bearing in mind that, high temperature accuracy (how close the converted temperature value being logged is to the true temperature being measured) is more difficult to achieve when compared to other types of measurement (the ITS-90 standard, upon which all current temperature measurements are based, is only accurate to 5 decimal places, and unlike some other standards, e.g. derived at atomic level, using unique methods, ITS-90 was derived using more precise variants, of generally used apparatus and methods, e.g. a gold standard PT100 sensor, the triple point of water, and other known preset points). However, high temperature precision (the smallest measurable difference between 2 temperature values) is easier to achieve, with your average Data Acquisition Device typically having a resolution (which is essentially the digital equivalent of precision) of at least 10 times it's accuracy. The resolution of the TC-08 is approximately 100 times it's accuracy. As you are interested in how the NTC sensor changes relative to a fixed resistance value, I would say that what you need is a measurement system capable of high precision, rather than high accuracy. However, for completeness, we will discuss both precision and accuracy.
You can now connect the logger to the Pi and remove the keyboard, mouse and video to make an inexpensive stand-alone logger storing its captured data locally on a Pi SD card and better still, utilising the Power over Ethernet (PoE) capability on the Raspberry Pi 4Bpaired with the PoE PiHAT not only eliminates the need for an external power supply and powered USB hub, it also internet-enables your logger at the same time
PicoScope 7 Early Access for Linux
It is a great scope. I had a weird problem - it did not work on one of my PC’s. Customer service gave me first class service. If I could give 6 stars for customer service - I would do so. Nothing in the help talks about Hardware drivers and nothing makes a connection even though it has the DLL and knows what and where it is. A general rule of thumb in data acquisition is that, if you want to perform a calibration/measurement of a measurement system you should use a calibration/measurement system that is at least 3 times as accurate as the system you are measuring. A 10K NTC therimistor (which has a typical accuracy* of ±0.1°C at 20°C) is considerably more accurate and stable than a thermocouple (which has a typical accuracy* of ±2.7°C at 20°C) for measuring the same temperature range. So, a thermocouple would be beyond it's limit of accuracy* in trying to log thermistor temperature against its resistance. PicoLog 6 alarms can also trigger a digital output on devices with supporting hardware, such as the PicoLog 1000 Series, ADC-24 and DrDAQ. You can even trigger a digital output from one of these devices based on an alarm condition from another connected logger without digital outputs, such as a TC-08. We have been using Picoscope 6404D for quite some time, and are amazed by its accuracy and powerful emulations while working with numerous signal evaluations.
Rather than webcam our benchtop scope screen, it was suggested we use a PicoScope to share waveforms via screen share.You can reduce the systematic uncertainties due to measurement session variation by repeatedly taking the same measurements. By doing all this, the difference in accuracy between the TC-08 and a high precision, high accuracy thermistor should be easy enough to overcome. The TC-08 thermocouple data acquisition module is designed to measure a wide range of temperatures using any thermocouple that terminates in a miniature size thermocouple connector. Additionally the TC-08 can also measure other sensors using a ±70 mV range. Featuring built-in cold junction compensation (CJC), the TC-08 has an effective measuring range of -270 to 1820°C (the actual temperature range depends on the thermocouple type being used). Pico Technology data loggers work great when USB connected to PCs running Windows, macOS and Linux, and now with support for Raspbian OS on armhfprocessors, we support Raspberry Pi computers.
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