Chapter 11: Sensor Verification
ValProbe RT User Manual 102
Chapter 11. Sensor Verification
11.1. Introduction and Overview
With the ValProbe RT system, sensors at up to six different temperature setpoints for
Pressure / Temperature Loggers, six different humidity setpoints for Humidity Loggers, may be
verified, though each sensor type must be verified independently.
The ValProbe RT uses the parameters defined in the Verification setup to perform sensor
verification. Verification parameters specify the temperature/humidity reference setpoints at
which Verification is performed, and the stability and deviation criteria for the
temperature/humidity sensors and the temperature/humidity standard. Temperature
Verification requires the use of a Kaye IRTD as the temperature standard. The IRTD’s
measurement accuracy is 0.025ºC, with a range of –196ºC to 420ºC. The software requires a
Temperature bath able to simulate the verification temperatures. If a Kaye bath is used, the
system can perform automatic Verification in which the bath temperatures are automatically
controlled. A manual Verification may be performed for non-Kaye baths. For adequate stability
and uniformity, use the correct bath (see Section 11.1.2).
Humidity Verification requires the use of a Humidity chamber. The first step in the Humidity
Verification process is to verify that the Humidity chamber is stable. Stability is the maximum
allowable change in Humidity for the humidity standard over the specified time interval. The
first set point is created with a default value of 90%RH but may be set between 5%RH –
95%RH. The maximum allowable change for the first set point is between 0.5%RH – 5.0%RH
and defaults to 0.5%RH, for set points 2-6, the range is the same, but the default setting is
1.0%RH (see Section 11.1.2).
Principle of Operation
When starting Verification, the ValProbe RT Loggers begins to collect data every ten seconds
to its internal memory for the duration of all defined setpoints. At the same time,
measurements from the IRTD/Humidity chamber are collected by the Base Station. The Base
Station uses the IRTD/Humidity chamber data, along with the specified criteria, to display and
determine stability at each setpoint. At the conclusion of the Verification, the data from
Loggers are read and the system calculates based on the Loggers and IRTD/Humidity
chamber data, whether the Loggers have met the defined stability and deviation criteria. The
ValProbe RT system generates a verification report for each sensor and setpoint – which is
stored as a .pdf file for Verification documentation printing.
When Verification is complete, the ValProbe RT system writes the Verification date into the
Logger and stores each Logger’s report file into the Console under the corresponding
equipment tile by Logger serial number.
Along with the date of the last Verification, the Logger also contains the Factory Calibration
date, including calibration offsets, inside the Logger’s non-volatile memory. This data remains
intact even if the battery is depleted or exchanged.
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