Adjustment Of Measurement Sensitivity To User Defined Reference; Figure 8 Sensitivity Calibration Plot (Example) - Michell Instruments Condumax II User Manual

Condumax II User's Manual
As shown above, the least squares regression of this plot can be utilized to set the Trip
Point. i.e. instrument measurement sensitivity. In the case shown a trip level of 275
mV would be determined.
3.3.4

Adjustment of Measurement Sensitivity to User Defined Reference

Condensate mode (see Section 3.3) is a useful feature if the customer decides to 'fi ne
tune' the Trip point to achieve a harmonized reading with a secondary measurement
device (such as Bureau of Mines dew-point apparatus applying ASTM D1142 method).
Secondary measurement device reads x HC dew point at pressure y (which must be
the analysis pressure required on the Condumax II). Set Condumax II to analysis
pressure y, and operate in Condensate Mode with Trip Temperature set to x, the value
measured by the secondary measurement devise. Allow the Condumax II to perform
at least 3 measurement cycles to assure measurement stability with constant sample
gas composition and optimum measurement cooling rate, <0.1°C/sec (observed in the
Status Page). Implement the harmonization of measurement sensitivity adjustment by
returning the Condumax II to normal Measurement Mode and setting the Trip Point to
the signal change mV value obtained in Condensate Mode.
The facility to adjust the Trip Point setting allows the user to harmonize on-line process
measurement sensitivity of the Condumax II with customer's preferred reference
method or to achieve conformance with any relevant regulatory standards that may
apply, most typically:
1. Bureau of Mines chilled-mirror dew point apparatus applying ASTM D1142.
2. Potential Hydrocarbon Liquid Content analysis (PHLC) applying ISO6570.
3. Measurements of synthesized natural gas mixture of certifi ed composition
with prediction of HC dew-point temperature from equation of state
calculation.
Michell Instruments
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
-20 -10
MIRROR TEMPERATURE Deg C
Sensitivity Calibration Plot (Example)
Figure 8
0 +10
OPERATION
23