Endress+Hauser HART Proline Promass 500, Special Documentation

Page: 39 / 52

Proline Promass 500 Use in protective systems
Hauser 39
6.3.5 Testing with a secondary standard (density)
Check measured value for density by comparing with a secondary standard. The measuring
device is checked consecutively in the empty state and with a medium of known density (e.g.
process medium or water).
I. Test sequence:
Check the measured values with a reference value (secondary standard or value from the
literature) when the device is installed, or check on a factory calibration rig once the device
has been removed.
The density measured values determined in each case are compared against the real density
of the media.
The reference values are compared against the measured values of the device under test
(DUT) using one of the following methods:
a. Comparison by reading off the digital measured value
Compare the digital measured value of the secondary standard against the measured value
display of the DUT at the logic subsystem (process control system or safety-related PLC).
b. Comparison of the measured value by measuring the current
1. Measure the current at the DUT using an external, traceably-calibrated ammeter.
 Note: measuring equipment requirements:
• DC current measuring uncertainty ±0.2 %
• DC current resolution 10 μA
2. Measure the current of the DUT at the logic subsystem (process control system or
safety-related PLC).
II. Assessment of the results:
The amount of deviation between the measured density and the reference value must not
exceed the measured error specified for the safety function.
‣
Follow the information in the section on "Restrictions for use in safety-related applications
– information on measured errors" →  16.