ACR Electronics SmartReader Plus Bedienungsanleitung PDF herunterladen (Seite 78)

SmartReader Data Loggers

4. Cover the bucket with foam chips or another suitable insulating material. Let sit for at

least five minutes while the temperature stabilizes and the thermistor has a chance to

respond. If the test is to continue for more than a few minutes, add more ice periodically,

as before, insuring that it is tightly packed to the bottom of the bucket each time. The

goal is to ensure that the thermistors are always in contact with an ice / water mixture

over their entire surface.

5. Measure the temperature of the water (it should be very close to 0°C) and the resistance

of the thermistor. This is the Low calibration point data.

6. Next, fill up a pot of water and heat it up till it reaches approximately 50°C. Once the

temperature and thermistor have stabilized, again take an accurate reading of both the

temperature and the thermistor's resistance, and record. This is the Mid calibration point

data,

7. Now heat the water so it boils. Record the temperature (100°C) and the resistance again.

This is the Mid calibration point data.

8. With TrendReader software, create a thermistor equation (using the equation wizard)

from the Equation Menu. Save the equation to the logger.

Note that the accuracy of the above test procedure is primarily limited by the cumulative

accuracy of the instruments you are using and how carefully you carry out the procedure. You

should, however, be able to achieve accuracies within ±1.0°C under most circumstances for

thermistors with R25 values of between 10k and 100k ohms. You can perform tests with

thermistors of other R25 values by using dry ice (for very low temperatures down to -70°C) or

an oven (for temperatures up to a maximum of 450°C).

To avoid damaging your thermistors, when calibrating, make sure to note the following:

· do not exceed the upper temperature limit rating for your high calibration point, and

· do not introduce the sensors to rapid changes in temperature (for example, from the ice

bucket right into the boiling water).

1.14.3 Relative Humidity Calibration

If you want to confirm the calibration of your RH sensor or EH-020A Temperature and Relative

Humidity probe, you can simply return it to your authorized sales representative or perform

your own field test using the special adjustment provisions in TrendReader software.

Recommended methods of calibration include using an accurate relative humidity test

chamber or by mixing saturated salt solutions. Both tests are performed at an ambient room

temperature of 20 to 25°C (68 to 77°F).

RH Chamber Test

If you intend to use a Relative Humidity Test Chamber for your calibration, make sure it has

been recently tested to within ±1%. The procedure to calibrate is as follows:

1. Set up your humidity data logger with a sample rate of 20 seconds and equation 38 on

the RH channels. Make sure you have selected Normalized Byte data units. If you are

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ACR Electronics SmartReader Plus Bedienungsanleitung Seite 78