The built-in temperature sensor in most modern hard drives can show incorrect results. The difference between the measured and actual temperature can be 7-9 degrees Celsius, and in some cases even more.

To solve this problem, it is recommended to measure the actual temperature of the hard drive using an external infrared thermometer or front panel with a temperature sensor. And then set the difference between the measured value and the temperature that the Hard Disk Sentinel displays (according to the disk itself) as a temperature offset. This is called calibration.

After measuring the actual temperature (with a thermometer or other external sensor), the offset can be calculated by subtracting the value specified by the program from the measured value. The offset can be positive (the program shows a lower temperature than the real one) or negative (otherwise).

This offset can be specified on the S.M.A.R.T. hard disk by selecting attribute No. 194 (hard disk temperature) and using the + / - buttons (by clicking on the number between these characters, you can directly enter the offset value for Celsius).

Hard Disk Sentinel automatically increments (or decrements) all reported hard drive temperatures according to configured offsets. Thus, the correct (real) temperature will be displayed in any case (for example, when comparing the temperature of a hard disk with a threshold value, when saving reports, etc.)

Note: if calibration is not possible (computer unit must not be opened), the expected offset value can be determined by comparing the first displayed temperature value immediately after starting the computer with the ambient temperature value (room, office). At this time, the CPU, video card or other components are not too hot and do not affect the hard disk temperature value. Of course, this is only true if the computer has been given enough time to cool down to ambient temperature (not turned on for about 8 hours).

For example, if the hard disk temperature is 17 degrees Celsius (immediately after starting the computer), and the room temperature is 22 degrees, then this difference (5) can be set as an offset value (because the hard disk cannot be cooler than the ambient temperature ) . This offset is better than nothing, but an external thermometer is still required to determine the proper temperature offset.

Note : temperature offset must be determined from Celsius , regardless of the selected temperature unit (Celsius or Fahrenheit).

Note: an unregistered version of the program automatically resets all offset values ​​to 0 if the user reboots the Hard Disk Sentinel.

Theoretical part

Temperature measurement is the most widespread type of measurement. In everyday practice, millions of thermometers of various types are used for various temperature measurement ranges. Conventionally, according to the ranges, thermometers can be divided into the following groups:

1. Thermometers for measuring room temperatures. This also includes devices for climatic measurements, since the latter do not fundamentally differ from purely room thermometers. Accordingly, the range of measured temperatures is from – 50 to – 40 ° C to the boiling point of water + 100 ° C.
2. Thermometers for measuring low (cryogenic) temperatures. Such devices operate on special principles, including the effects of superconductivity. Real cryogenic temperatures range from close to zero to temperatures at which mercury and alcohol freeze. In this case, climatic thermometers become unsuitable for measurements.
3. Thermometers for measuring high temperatures actually operate in the range from several hundred degrees Celsius to the melting point of gold of 1064.18 ° C. Most often, thermocouples and resistance thermometers are used to measure such temperatures.
4. Thermometers for measuring the temperatures at which objects become self-luminous, i.e. emit light visible to the human eye. Such devices are called pyrometers, which comes from the word "pyro" - fire. They are used to measure the temperatures of incandescent objects, flames or plasmas. The human eye sees temperature radiation, starting from a temperature of 800 - 900 ° C, when the radiation of objects is seen as dark cherry.
5. To measure temperatures of thousands, tens and hundreds of thousands of degrees, special spectroscopic methods for measuring temperatures are used, in which the latter is determined by the intensity of the spectral lines of the atoms and ions that make up the object. Such a state is called plasma, and methods for measuring plasma temperature are called diagnostic methods. In the same way, the temperature of celestial self-luminous objects - stars - is determined.

According to the implementation of temperature measurement methods, the following methods are distinguished, when the thermometer is brought into direct contact with the body whose temperature is measured, and non-contact methods, when the source of information about the temperature of the object is the luminosity, brightness or color of the object.

Contact thermometers for measuring room and average temperatures can be divided into the following types:

• Volumetric instruments, in which information about the temperature is obtained by changing the volume of a thermometric liquid or gas. This is the most common type of thermometer, well known to everyone.
• Dilatometric thermometers, in which the temperature is measured by the linear expansion of bodies. The most popular thermometers of this type are bimetallic plates, which are two strips of metals with different thermal expansion coefficients, connected (soldered) along the entire length (Fig. 1).

Bimetal plate - temperature sensor

Bimetal temperature sensors are very convenient for automatic control devices and are widely used in various temperature controllers.

Thermocouples as temperature sensors. In these thermometers, the temperature is judged by the EMF that occurs in a circuit consisting of two different conductors soldered at the ends. If the junctions are maintained at different temperatures, a current appears in the circuit (Fig. 2) proportional to the temperature difference between the junctions.

Differential thermocouple.

Thermal resistance - temperature sensors in the form of a metal wire that changes electrical resistance with temperature changes. The dependence of resistance on temperature has the form:

where R T is the resistance at temperature T 1 . R 0 - resistance at 0 0 C, a - temperature coefficient is positive for metals and negative for graphite.

Thermometers for measuring low temperatures, as well as pyrometers and methods for diagnosing plasma, have a number of features, the essence of which goes beyond the limits of the specific problem posed. Those who wish can familiarize themselves with this in more detail in the specialized literature.

To understand the essence of the problem posed in the work, it is necessary to dwell in detail on the accuracy capabilities of contact thermometers.

The most accurate of all types of contact thermometers are resistance thermocouples. The electrical resistance of some metals, such as platinum or rhodium, is very stable over time. This makes it possible to calibrate the thermistor with confidence that its resistance at a given temperature remains constant for almost the entire life of the thermometer. Platinum resistance thermometers in measuring and metrological practice are a means of transferring the size of a temperature unit from standards to working measuring instruments, i.e. most often used as exemplary means of measurement.

Some types of thermocouples are next in temperature measurement accuracy. For example, a thermocouple made of platinum (one of the electrodes) and an alloy of platinum with 10% rhodium or 15% rhodium (the second element of the thermocouple) has a temperature dependence of the EMF for various specimens, reproduced in 4 - 5 digits. This accuracy is guaranteed regardless of thermocouple size, electrode thickness, wire technology, etc.

Other types of thermocouples, eg chromel-aluminum, chromel-…. copper - constantan, iron constantan, etc. have large absolute values ​​of thermo EMF, but they need individual calibration, since the properties of such thermocouples are individual for each sensor.

Volumetric thermometers usually allow you to measure temperature with an error of 0.1 - 0.05 0 C, i.e. guarantee accuracy in 1 - 2 decimal places. For this reason, volumetric instruments are used for the most part in routine everyday measurements when the specified accuracy is sufficient. This takes place when measuring temperature in rooms, outdoors, in process control, etc.

Dilatometric thermometers have measurement errors at the level of 1 - 2 0 С and for this reason are used in measurements that do not require high accuracy. If we are talking about temperature control in freezers, in engine cooling systems, when heating water and in other similar tasks, then dilatometric thermometers are the most preferable due to their high mechanical strength, durability, and reliability. These qualities are the reason why dilatometric thermometers or dilatometric sensors are installed in many automatic temperature control systems - in refrigerators, in cars, in machines and mechanisms, when temperature information is required.

Concluding a brief review of contact methods for measuring temperature, let us recall the main metrological categories in any type of measurement. Let's start with definitions:

• standard. the original exemplary measuring instrument, the highest accuracy setting, depending on the metrological status, is a measuring instrument that allows you to reproduce a unit of physical quantity and (or) measure it with the highest possible accuracy
• exemplary measuring instrument called a measuring instrument intended for verification of working measuring instruments. An exemplary measuring instrument can be one of the working instruments with a more accurate comparison with the latest defined metrological characteristics.
• working instruments– measuring devices directly used in measuring procedures
• measures- measuring instruments designed to store and transmit the size of a physical quantity. Measures are used to transfer the size of a unit from standards to exemplary measuring instruments or from exemplary means to workers.

The process of transferring the size of a unit can be carried out using an exemplary measure or by comparing (comparing) the readings of a working device with the readings of an exemplary device. Calibration and graduation of thermometers can also be carried out:

1. According to standard reference data, for example, about the EMF of thermocouples or tabular values ​​of the resistance of reference thermometers.
2. According to reference temperature points, i.e. according to standard values ​​of phase transition temperatures - boiling, solidification, melting, pure substances. In total, the temperature scale MPTSh - 90, currently operating in the SI system, contains 27 temperature values ​​in the range from -259.346 0 C to 33.83 0 C. Among these values, 14 reference points are considered basic, i.e. have an error of 2 - 3 decimal places. The remaining 13 reference points have an error of tenths of a degree of 0 C and above.

The purpose of the work and description of the measuring installation

The purpose of this work is to familiarize with the metrological aspects of temperature measurements - with the procedure for transferring the size of a unit of thermodynamic temperature from a reference thermometer to a working device. A platinum resistance thermometer, certified with an error of 0.05 0 С, was chosen as an exemplary measuring instrument. The thermal resistance, intended for use in thermometers with a measurement error of 0.1 0 С, is used as a measuring instrument. platinum thermistor with copper thermistor.

Another purpose of the work is to calibrate the working thermistor and determine the temperature coefficient l in formula 1 for it.

The passport value of the resistance of a platinum temperature sensor in the range from –50 0 С to 200 0 С is used as initial information. These data are given in Table 1 and shown in the graph in Fig. 3.

Resistance of the platinum temperature sensor in the range - 50 0 C - +200 0 C. Passport data.

NTC (Negative Temperature Coefficient Thermistors) and PTC (Positive Temperature Coefficient Thermistors) are temperature dependent resistors. To measure resistance, it is connected in series with an ordinary resistor and the voltage drop across it is measured. An example connection diagram is here.

A microcircuit that delivers 10mV per degree Kelvin. Available in various designs. Examples of connection diagrams are given in the datasheet; the scheme of work with the comparator (instead of the "correct" ADC) is here.

1 degree accuracy (at 25°C) even without calibration

too many ripples are induced in the case of long connecting cables

An IC like the LM335, with the difference that the current flowing through the IC is proportional to the temperature. Using the "circuit" (two resistances) from the datasheet, you can change the current in such a way that 1 mV will be issued for each degree Kelvin. Since the current/voltage conversion takes place on the board (and therefore close to the ADC) and the measurement is made using current, the interference due to mains ripple is much less than in the case of the LM335

1° accuracy (at 25°C) even without calibration

relatively low price (Reichelt 0.90 EUR)

ADC required

DS1621 is a temperature sensor combined with an ADC. It transmits the measurement results via the I2C bus. Schematic diagram of an electronic thermometer using this chip is here.

Advantages:

already calibrated

no need for ADC

since I2C is a bus, with just two I/O ports, you can connect and use multiple DS1621 and other I2C chips

The LM75 is similar to the DS1621 but is only available in an SMD package and has lower accuracy. However, it is more often seen on PC motherboards, so when disassembling an old machine, you can get a thermal sensor at your disposal for free. The wiring diagram is here.

relatively expensive (Reichelt 5.45 EUR)

SHT11 is a temperature and humidity sensor from Sensirion.

How to determine the type of SKS Sensors® temperature sensor?

The type of SKS Sensors® temperature sensor is represented by a set of symbols - a code. The code for each sensor type can be found in the product documentation, see individual types 1 to 22 in section Products > Temperature sensors .

Create your product code SKS Sensors ® with product selection tool

You can step by step create the correct product code for your application by selecting the properties in sequence and entering the basic sizing data into the appropriate fields of the Product Selector Tool.

If you need help converting an old sensor type to a new one, please contact your sensor dealer SKS Sensors ® .

Application #4: Temperature sensor calibration.

Upon release from production, the temperature sensor built into the amperometric sensor is calibrated according to the procedure, the execution algorithm of which is recorded in the service menu of the analyzer. You should only calibrate the temperature sensor when replacing the sensor with a new one. In this case, connect the new sensor to the measuring device and turn on the analyzer. To calibrate the temperature sensor, you need to assemble the installation shown in the figure. With this setting, you need to provide three temperature scale marks in the range of 5 -50 ° C. If your laboratory does not have a thermostat, you can provide three temperature scale marks in an easier way. To do this, you need a thermos, a glass of distilled water at room temperature and a plastic glass with ice. Pour distilled water heated to 50 +5 ° C into a thermos. Make a hole with a diameter of 10 mm in a glass with ice. To increase the diameter of this hole to 16 mm, pour warm water into it. After 5-10 minutes, the water in the hole will have an ice melting temperature of ~ 0 o C.

To calibrate the temperature sensor, go to the service calibration menu. To do this, enter the Calibration menu and, while holding the "DOWN" key, press the "ENTER" key. In the service menu that appears, select the "TEMPERATURES" option, press "ENTER".

In the window that opens, select the "Low point" option and press "ENTER".

Immerse the sensor and the reference thermometer in a temperature-controlled beaker with a temperature of the bottom mark of the scale: 5 + 1 o C or in a well in a beaker with ice.

In the window that opens, enter the temperature of the low point using the cursor keys and press "ENTER".

After a successful low point calibration message, the temperature sensor calibration menu will reappear on the screen. Select the Top Point option and press ENTER.

Immerse the sensor and the reference thermometer in a temperature-controlled beaker or thermos with the temperature of the top mark of the scale and, after waiting for the thermometer readings to settle, press "ENTER".

Read the reference thermometer reading and use the cursor keys to enter this value.

If the high point calibration is successful, the temperature sensor calibration menu will reappear on the screen. Select the "T Correction" option and press "ENTER".

Follow the instructions shown on the analyzer display and press ENTER.

Wait until the thermometer readings are established and press "ENTER".

Read the temperature reading from the reference thermometer and enter this value using the keypad. Press "ENTER".

For certain control purposes, such as control of a heating plant, it may be important to measure the temperature difference. This measurement can be carried out, in particular, by the difference between the outside and inside temperatures or the inlet and outlet temperatures.

Rice. 7.37. Measuring bridge for determining the absolute values ​​of temperature and temperature difference at 2 points; U Br is the bridge voltage.

The principal device of the measuring circuit is shown in fig. 7.37. The scheme consists of two Wheatstone bridges, and the middle branch (R3 - R4) of both bridges is used. The voltage between points 1 and 2 indicates the temperature difference between Sensors 1 and 2, while the voltage between points 2 and 3 corresponds to the temperature of Sensor 2, and between points 3 and 1 the temperature of Sensor 1.

Simultaneous measurement of temperature T 1 or T 2 and temperature difference T 1 - T 2 is important in determining the thermal efficiency of a heat engine (Carnot process). As you know, the efficiency W is obtained from the equation W \u003d (T 1 - T 2) / T 1 \u003d ∆T) / T 1.

Thus, to determine, you only need to find the ratio of the two voltages ∆U D 2 and ∆U D 1 between points 1 and 2 and between points 2 and 3.

Precise adjustment of the described temperature measuring instruments requires rather expensive calibration devices. For the temperature range 0...100°C, quite accessible reference temperatures are available to the user, since 0°C or 100°C, by definition, are respectively the points of crystallization or boiling point of pure water.

Calibration at 0°C (273.15°K) is carried out in water with melting ice. To do this, an insulated vessel (for example, a thermos) is filled with heavily crushed pieces of ice and filled with water. After a few minutes, the temperature in this bath reaches exactly 0°C. By immersing the temperature sensor in this bath, the sensor readings corresponding to 0°C are obtained.

The same applies for calibration at 100°C (373.15 K). A metal vessel (for example, a saucepan) is half filled with water. The vessel, of course, should not have any deposits (scale) on the inner walls. By heating the vessel on the stove, bring the water to a boil and thereby reach the 100-degree mark, which serves as the second calibration point for the electronic thermometer.

To check the linearity of a sensor calibrated in this way, at least one more control point is required, which should be located as close as possible to the middle of the measured range (about 50 ° C).

To do this, the heated water is again cooled to the specified area and its temperature is accurately determined using a calibrated mercury thermometer with an accuracy of 0.1°C. In the temperature range of about 40 ° C, it is convenient to use a medical thermometer for this purpose. By accurately measuring the water temperature and the output voltage, a third reference point is obtained, which can be considered as a measure of the linearity of the sensor.

Two different sensors, calibrated by the method described above, give identical readings at points P 1 and P 2, despite their different characteristics (Fig. 7.38). An additional measurement, such as body temperature, reveals the non-linearity of the characteristic AT sensor 2 at point P 1 . Linear characteristic BUT sensor 1 at point P 3 corresponds exactly to 36.5% of the total voltage in the measured range, while the non-linear characteristic B corresponds to a clearly lower voltage.

Rice. 7.38. Determination of the linearity of the characteristics of the sensor with a range of 0...100ºС. Linear ( BUT) and nonlinear ( AT) the characteristics of the sensors coincide at the reference points of 0 and 100ºС.

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Temperature sensors made of platinum and nickel

Thermocouples

Silicon temperature sensors

Integrated temperature sensors

temperature controller

NTC thermistors

PTC thermistors

PTC thermistor level sensor

Temperature difference measurement and sensor calibration

PRESSURE, FLOW AND SPEED SENSORS

Like temperature sensors, pressure sensors are among the most widely used in technology. However, for non-professionals, pressure measurement is of less interest, since existing pressure sensors are relatively expensive and have only limited use. Despite this, consider some options for their use.

Agreed I approve

Head of GCI SI Director

Deputy Director of FGU VTsSM

__________ __________

Calibration Method

temperature sensors of the KDT series.

Developed

Ch. technologist LLC "CONTEL"

Calibration Method for Temperature Sensors

KDT-50, KDT-200 and KDT-500.

1. Before starting calibration, check the compliance of the components located on the board according to the assembly drawing: KDT50.02.01SB - for KDT-50 sensors; KDT200.02.01SB - for sensors KDT-200; KDT500.02.01SB – for KDT-500 sensors.

2. Calibration of the electronic block of sensors KDT-50 and KDT-200.

2.1. Connect to the board the power supply and the equivalent of the thermometer - resistance TCM-100 according to Fig.1.

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2.3. The sequence of adjustment operations.

2.3.1.Set the voltmeter mode "U=" and the measurement limit corresponding to the value "three decimal places".

2.3.2. Set the lower value of the measured temperature on the TCM equivalent: for KDT-50 - "-500C", for KDT-200 - "00C".

2.3.3.Apply power supply.

2.3.4. Rotate the trimmer resistor RP1 to set the value of the output current 4 mA(voltmeter reading 0.400).

2.3.5. Set the upper value of the measured temperature on the TCM equivalent: for KDT-50 - "+500С", for KDT-200 - "+2000С".

2.3.6. Rotate the trimmer resistor RP2 to set the value of the output current 20 mA(voltmeter reading 20.00).

2.3.7. Repeat the operations of items 2.3.4 and 2.3.6 until the output current is established corresponding to the range

measured temperature within the error not exceeding 0,25% .

2.3.8.Check linearity at intermediate points.

2.3.9 Correspondence of measured temperature (equivalent value of resistance) and output current are given in Appendix 1.

3. Calibration of temperature sensors KDT-500.

3.1. Connect to the board the power supply and the equivalent of the thermometer - resistance Pt-100 according to Fig.2.

The polarity of the power supply connection does not matter.

-EquivalentPt100 - a special resistance box simulating a resistance thermometer of the Pt-100 type;

-V- Digital voltmeter type B7-40;

-Rn- electrical resistance coil R331;

-IP- stabilized direct current source type B5-45.

3.2 Sequence of calibration operations.

Due to the absence of adjusting elements in the product, the calibration operation is reduced to checking the operability and linearity of the conversion of resistance into current.

3.2.1. Set the voltmeter mode "U =" and the measurement limit corresponding to the value "three decimal places".

3.2.2. Set the lower value of the measured temperature on the Pt-100 equivalent: "00С".

3.2.3. Apply supply voltage.

3.2.4. Voltmeter readings must comply with 4 mA+/-0,25% (voltmeter reading 0.400).

3.3.5. Set the upper value of the measured temperature on the Pt-100 equivalent: "+5000С".

3.3.6. Voltmeter readings should correspond to 20 mA+/-0,25% (voltmeter reading 20.00).

3.3.7. Check linearity at intermediate points.

3.3.9 Correspondence of measured temperature (equivalent value of resistance) and output current are given in Appendix 2.

Note. The temperature sensor circuit KDT-500 is designed to work together with Pt-100 with W100=1.3910. The use of a resistance thermometer with W100=1.3850 leads to an increase in the basic error to 0.8% in the middle of the range.

4. After adjustment, the sensor boards are varnished. The recommended drying time is 2 days.

After drying, the boards are subject to mandatory rechecking in order to correct the output current. During this operation, it is enough to check the sensor at the ends of the range.

Executor________

Attachment 1

Correspondence of temperature, equivalent resistance and output current of KDT-50 temperature sensors.

Correspondence of temperature, equivalent resistance and output current of KDT-200 temperature sensors.

In the absence of an equivalent of TCM-100, a resistance box MCP-63 or similar should be used.

Appendix 2

Correspondence of temperature, equivalent resistance and output current of KDT-500 temperature sensors.

(for W100=1.3850)

In the absence of a Pt-100 equivalent, an MSR-63 resistance box or similar should be used.