Author: GER Electronics

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Notes on Temperature Sensors

Notes on Temperature measurement and sensors.

1. As of May 20,2019, the International System of Units (SI) was redefined and adopted.
In this adoption, all base units of measure (length, time, mass, electrical current, thermodynamic temperature, amount of substance, luminous intensity) have been defined by the seven natural constants (speed of light, Planck constant, elementary charge, Boltzmann constant, Avogadro constant, luminous efficacy constant and hyperfine transition frequency of Cesium). The International Temperature Scale (ITS-90) reflects the thermodynamic temperature scale, expressed in degrees Kelvin, by a series of reference points. Each point is a physical state of a material, such as hydrogen triple point (0K or -259.34C) and the freezing point of platinum (2042.15K or 1769.00C) .

2. In US, the organization responsible for all thermometry standards, research and calibration is NIST (National Institute of Standards & Technology). Its Thermodynamic metrology group maintains and develops national standards of temperature and supports of all types of contact thermometers calibration methods. https://www.nist.gov/pml/weights-and-measures/metric-si/si-units

3. There are two classes of temperature sensors: absolute and relative class. The absolute temperature sensors have a reference calibration point such as absolute zero on the thermodynamic scale, or any other reference point such as “ice water triple point”. Some examples of absolute sensors are RTDs and thermistors. An example of the relative sensor class are thermocouples. The thermocouple has to have a “reference junction” placed at a known temperature to measure the difference between the junction and the point of measurement. https://gerelectronics.com/usb-temperature-sensor/

4. A very large majority of all temperature sensors used in commerce and industry are thermocouples, RTD and thermistors.

5. All temperature sensors utilize a natural phenomenon that were discovered in the last few centuries and then studied and quantified scientifically. For example, in 1821, Thomas Johann Seebeck, accidentally observed that by joining wires of different metals end to end, there was a magnetic disturbance detected by his compass. This knowledge stayed unexplored until 1826 when A.C. Becquerel suggested that Seebeck’s effect could be used to measure temperature. It took another 60 years for the first thermocouple temperature sensor to be constructed by Henry LeChatelier.

6. Today the thermocouple temperature sensors are characterized by American Standards ANSI MC 96.1. https://blog.ansi.org/2018/10/thermocouples-calibration-table-ansi-mc961/

7. At about the same time, in 1887, Hugh Callendar published a paper describing how to use platinum as a temperature sensor. This platinum sensor was markedly different from the thermocouple as it utilized a physical property of platinum and other metals called thermo-resistivity. The thermo-resistive effect was first noted by Sir Humpry Davy in 1821. The RTD, as it is called nowadays, is an absolute sensor. https://gerelectronics.com/usb-temperature-sensor/

8. Thermistors have come to use in more recent times. It name is an abbreviation of “thermal resistor”. They are based on the same thermo-resistance effects discovered in the 1800’. However, they are not made of pure metals, but of metal oxides. Its temperature response (or transfer function) depends on its physical dimensions and the intrinsic resistivity of the metal oxide. After many years of experimental measurements, the relationship between the resistance and absolute temperature for a thermistor has been agreed to be a non-linear equation of the logarithm of thermistors resistance, R, and a polynomial equation of third order in temperature, T. For practical temperature measurements, because the equation is non-linear, the selection of the measurement range becomes of paramount importance. https://gerelectronics.com/usb-temperature-sensor/

9. In the following posts we will describe each of these devices in more details.

 

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New wireless microHUB from Yoctopuce SARL.

COMING SOON!

Connect multiple sensors to a LTE cellular network!

The new long-range YoctoHub based on the LTE technology. It supports the LTE-M (LTE Cat. M1) and NB-IoT (LTE Cat. NB1) standards. We selected these technologies because they are the easiest to implement for small and medium-sized businesses. Indeed, the YoctoHub doesn’t require setting up any particular infrastructure, nor any complex contract with telecom providers: a simple SIM card covering these technologies is enough.

Worldwide coverage for these networks is good, and the module allows you to accommodate frequency bands used in the different regions of the world. Unlike the LoRa and Sigfox networks using unlicensed frequency bands, the LTE technologies have a certain guarantee of stability thanks to the fact that the bandwidth use is controlled by the providers. The benefit is reduced risk of a decrease in the signal/noise ratio as and when other long-range networks deploy on the same frequency domain.

Hub 4G/LTE
The new YoctoHub-GSM-4G

The YoctoHub-GSM-4G will replace the YoctoHub-GSM-3G-EU and of the YoctoHub-GSM-3G-NA.  at a lower price point.

Moreover, it consumes somewhat less current, and when the coverage is good, it connects faster. In countries where LTE-M coverage is not available, the NB-IoT bandwidth is lower than that of 3G. For simple HTTP callbacks, it normally is not an issue.

For less technologically advanced countries which have neither LTE-M nor NB-IoT, the module can connect to a 2G network (GPRS or EDGE) on the four most widely used frequency bands.

For full specifications please visit https://gerelectronics.com/product/yoctohub-gsm-4g-lte/.

 

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Beta Test Offer!

For several years, we have been offering different YoctoHubs to connect Yoctopuce USB sensors directly to a network, without using a computer. But as you may have noticed, we didn’t throw ourselves headlong into cutting-edge technologies, especially when standards are split: LoRa, Sigfox, LTE-M, NB-IoT, 5G… With the multiplication of networks aimed at the IoT, we had to wait for the landscape to become clearer, because we couldn’t do it all and we had to choose the solution which would best suit our customers. But here it is, we finally made our choice, and it’s almost ready.

The new long-range YoctoHub is based on the LTE technology, on which the 4G and 5G networks are based. It supports the LTE-M (LTE Cat. M1) and NB-IoT (LTE Cat. NB1) standards. We selected these technologies because they are the easiest to implement for small and medium-sized businesses. Indeed, the YoctoHub doesn’t require setting up any particular infrastructure, nor any complex contract with telecom providers: a simple SIM card covering these technologies is enough, as previously with 2G and 3G technologies.

The worldwide coverage for these networks is good, and the module allows you to accommodate frequency bands used in the different regions of the world. Unlike the LoRa and Sigfox networks using unlicensed frequency bands, the LTE technologies have a certain guarantee of stability thanks to the fact that the bandwidth use is controlled by the providers. The benefit is reduced risk of a lowering of the signal/noise ratio as and when other long-range networks deploy on the same frequency domain.

The new YoctoHub-GSM-4G

Apart from the technology which changes, the functions of the YoctoHub-GSM-4G are essentially the same as that of the YoctoHub-GSM-3G-EU and of the YoctoHub-GSM-3G-NA. These two products are going to be replaced by the new one, which we can even sell at a lower price point than its predecessors. Moreover, it consumes somewhat less current, and when the coverage is good, it connects faster. The only disadvantage, if you are in a country where LTE-M coverage is not available, is that the NB-IoT bandwidth is lower than that of 3G. But for simple HTTP callbacks, it normally is not an issue. For less technologically advanced countries which have neither LTE-M nor NB-IoT, the module can connect to a 2G network (GPRS or EDGE) on the four most widely used frequency bands around the world.

At this point in time, we are looking for some Beta-testers in different countries to make sure that it works globally. If you think that you’ll need this module in the future, here is our offer:
• We sell you a new functional module for only $40, which is an 80% discount.
• You start testing the module in the next 1-2 weeks, to either confirm that it works well or to signal potential problems so that we can correct them with an update.
• If a hardware modification are required to solve an issue, you’ll receive a corrected version free of charge. Thus, at the end of the test period, you’ll have a fully functional hardware.
Interesting, isn’t it? So, contact us at info@greenenergyresearch.com to register for the Beta-test, telling us the region intended for the deployment, the type of network that you think you are going to use (NB-IoT or LTE-M), and if you already know which phone provider you are going to work with.

The offer is limited to one or two Beta-tests by network type and by country. This offer is on a first come, first serve basis!

All decisions are made by Yoctopuce SARL and are final.

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Phidgets announces availability of the new VINT networking modules.

What Is VINT?

VINT stands for Versatile Interface, and it’s the system that all modern Phidgets use to communicate. Everything is backwards compatible and we still support all direct-to-USB Phidgets. A VINT Hub is a Phidget that has a number of VINT ports than can be used to connect to other Phidgets, or directly to switches, LEDs or sensors. The main advantages of VINT are versatility, modularity, connectivity and stability.

 

 

 

Versatility

A VINT Hub Port is a versatile interface that combines the functionality of analog inputs, digital inputs, and digital outputs. It uses the same connector type as Phidgets Analog Inputs, so you can use the same sensor cables that came with those sensors. The mode of each port can be selected in software by creating a new object and opening it on the desired port. This allows for maximum flexibility and ensures that you can make the most of the ports on your hub. For information on the differences between VINT Ports and Analog Inputs, go to the Phidgets Connectors page

Modularity

VINT Hub Phidget

In the past, we needed to strike a delicate balance when it came to adding inputs and outputs to our Phidgets. Include too few, and users would need to buy additional InterfaceKits for their project. Add too many, and users would be forced to pay for the increased cost of the Phidget. Due to the versatility of VINT, you can program a VINT Hub’s ports to behave as whatever your project needs. For example, if you only needed digital outputs, you could set all six ports to digital output mode. If you need more than six inputs or outputs, you can buy an intelligent VINT device to expand the number of inputs or outputs you have. The bottom line is that nobody has to pay for extra functionality they’ll never use, and the users that need extra won’t be paying any more than before since all of the I/O modules are competitively priced.

 

Connectivity

While the InterfaceKit was often the center of a Phidgets system, there were many Phidgets that were too complicated to connect through simple analog and digital ports: Accelerometers, LED controllers, motor controllers, and thermocouple adapters, just to name a few. As a result, larger Phidgets systems tended to sprawl, taking up several of your computer’s USB ports and sometimes causing reach problems due to the maximum USB cable distance of 5 meters. This has all changed with VINT; intelligent VINT versions of these complicated Phidgets have been made, so you can connect them directly to a VINT Hub Phidget with ordinary 3-wire sensor cables.

Of course, you can still use other USB-connected Phidgets alongside the VINT Hub Phidget if you want, and you can control both from the same program.

Stability

An example of isolation on a VINT device. The orange regions illustrate the two isolated halves of the board. The chips that straddle the halves on the top and bottom are optocouplers that transmit the communication from your PC to the processor on the board. The chip in the middle also straddles the two halves, but this chip has internally isolated these two pins from the rest of them.

Normally, an analog sensor operates by measuring its surroundings, converting that measurement into a voltage between 0 and 5 volts, and pulling its data line up to that voltage. The advantage to a system like this is that it’s simple and usually compatible with other systems. One major downside, however, is how vulnerable this signal is to electromagnetic interference. A strong magnetic field produced by a running motor, the arc on a mechanical relay, or other mechanisms in the system can push the voltage on the data line up and down, resulting in inaccurate data. VINT communications avoid this problem by communicating using a protocol rather than a raw voltage. If the electromagnetic interference is great enough, the sensor may drop a data packet or two, but will soon resume sending data. This way, you can be sure that any data you receive is unaffected by interference.

Many VINT devices also come built-in with data and power isolation to prevent power fluctuations from entering the system. These fluctuations can cause unreliability by distorting reference values and in serious cases, damage parts of the system. These kinds of problems normally occur when multiple devices are powered by the same supply and current from the ground of one device enters other systems, or generally any application where small, sensitive components and high-power electronics need to coexist in the same system. An attached VINT device that has isolation built-in can be thought of an entirely separate circuit, since power is provided via a small transformer and data is transmitted with an opto-coupler.

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An update from Yoctopuce.

As part of our effort to continuously improve our products, we are currently updating a number of them in order to apply the recommendations of IEC 61010-1 standard. This change is important in particular for devices that may be connected to the mains (240 V AC).

For these products, we are switching from a simple functional insulation (340V) to a reinforced safety insulation (3 kV),that ensures that even in case of transient over voltage thelow voltage circuits and the USB bus remain safe. The device documentation will be updated accordingly, including safety
recommendations.

The products affested by this change are:
– Yocto-Watt
– Yocto-Volt
– Yocto-Amp
– Yocto-PowerRelay
– Yocto-MaxiPowerRelay

The change has already been completed for the Yocto-Watt. It has no impact on the device dimensions, nor on its pricing. You can find pictures of the new Rev. B on the product page, as well as the updated documentation. Same URL as before: http://www.yoctopuce.com/EN/products/usb-electrical-sensors/yocto-watt

We are about to proceed to similar changes for the Yocto-Volt, Yocto-Amp, Yocto-PowerRelay and Yocto-MaxiPowerRelay within the coming 1-3 weeks.

For the Yocto-Amp and Yocto-Volt, this enhancement will unfortunately come with a price increase (+8.5%), as a change of PCB material was the only way to bring the proper level of insulation without modifying the device size.

On the Yocto-PowerRelay, the change will have no impact on pricing nor on dimensions, but to maintain the proper distance between PCB tracks, we had to swap the position of outputs A and B. Since this is a
functional change, the new version will be named Yocto-PowerRelay-V2. The old Yocto-PowerRelay will still be available for some time if needed.

On the Yocto-MaxiPowerRelay, the change will have no impact on pricing nor on dimensions. We had to remove the extra 2.5mm fixing hole in the center of the device, but the outer 3mm fixing holes remain unchanged, as well as the terminal blocks.

Note that other products such as the Yocto-LatchedRelay, Yocto-MaxiCoupler, etc will remain unchanged for now, but the documentation will expressly state that their use on the mains is possibly dangerous as they will not get a reinforced safety insulation.

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