Fluke Hart Scientific 1575 Super-Thermometer, Руководство пользователя

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6.2.1 Maintaining Accuracy
There are many potential problems that can lead to inaccurate results when us-
ing the 1575/1590. Some of these are: improper calibration of the 1575/1590,
incorrect setup of the 1575/1590 parameters, wrong probe characterization co-
efficients, a damaged probe or sensor, poor connection of the probe wires, or
misuse of the 1575/1590. Always be alert to anything that may be wrong and
always try to verify your results. When possible, perform regular checks to ver-
ify the accuracy of your measurements. Consider the following suggestions:
1. Maintain calibration of the 1575/1590. It is recommended that the
1575/1590 be calibrated at intervals no greater than one year. For new
units the calibration interval should be six months for the first year. On a
more frequent basis, you can verify the resistance accuracy using stan-
dard calibrated resistors. This is most important when the 1575/1590 is
used in applications where accuracy is especially critical. (Section 9 ex-
plains how to calibrate or verify the accuracy of the 1575/1590.)
2. Double-check the reference resistor and current. Proper selection of
the reference resistor and driving current is very important to achieve full
accuracy. You should always verify the reference resistor and current se-
lection before making measurements. Consider displaying the reference
resistance and current in the programmable data fields so that they can be
readily checked (see Section 7.5.3).
3.
Set the digital filter correctly. The digital filter helps to improve resolu-
tion and accuracy. If it not set up properly the filter can be ineffective. A
common mistake is to set the filter threshold too low. This can cause the
filter to reset too often allowing excessive noise to pass through (see Sec-
tion 7.2.4). The message “FILTER RESET” helps alert you if this is a
problem.
4.
Check the probe coefficients carefully. Using the wrong probe coeffi-
cients can cause significant error with temperature measurements. Al-
ways verify that the correct characterization coefficients are being used.
It is good practice to display the probe serial number in one of the pro-
grammable data fields to help you verify that the correct parameters are
associated with the probe being measured (see Section 7.5.3). You can
use the CONV TEST function to test calculations of temperature with
the probe coefficients (see Section 7.4.4.5).
5. Use the parameter lock-out feature to protect critical parameters.
Set up the parameter safety lock-out to prevent access to critical parame-
ters such as the reference resistor calibration values (see Section 7.6.5.4).
This will help protect these parameters from being inadvertently
changed.
6.
Compare measurements of your working SPRT to a backup SPRT.
Resistance thermometers, especially SPRTs are very fragile and can eas-
ily be damaged or lose accuracy if mishandled. They are susceptible to
thermal shock and contamination. Periodically check your working
31
6 General Operation
Suggestions for Best Results