Measurement Specialties 9116 user manual Chapter Calibration Introduction, Ptv

Pressure Systems, Inc. Model 9116 User’s Manual

Chapter 4

Calibration

4.1Introduction

Each internal DH200 transducer in a Model 9116 Intelligent Pressure Scanner contains non- volatile read/write memory capable of storing the transducer's full thermal and pressure calibration data.

The Model 9116 Intelligent Pressure Scanner module uses a third-order polynomial to convert transducer output voltage to pressure. All calculations are carried out internally using high precision math. The following formula is used for all pressure output calculations.

PT(V)	=	[C0(T) + C1(T)*V + C2(T)*V2 + C3(T)*V3] * C SPAN - CRZ
where:
PT	=	Calculated applied pressure
V	=	Transducer output voltage
C0(T) .. C3(T)	= Conversion coefficients generated from calibration data at
CRZ		temperature T.
	=	Re-zero adjustment’s “offset”correction coefficient
CSPAN	=	Span adjustment’s “gain” correction coefficient

Since the polynomial’s coefficients are a function of the current temperature, they are dynamically re-calculated by the module firmware (with other equations) to compensate for each transducer’s measured temperature change.

Each Model 9116 Intelligent Pressure Scanner contains an integral purge/leak check calibration manifold. Through software commands, this valve may be placed in one of four positions: RUN, CAL, PURGE, or LEAK-CHARGE. (See the Set/Do Operating Options/Functions (‘w’) command (ii=0C & 12) in Chapter 3, and in particular the Valve Position Chart at the end of command’s description.) When each module’s internal calibration valve is placed in the CAL/RE-ZEROposition (through software commands), all DH200 transducer pressure inputs are pneumatically connected to the CAL input ports. All DH200 reference inputs are pneumatically connected to the CAL REF input port. The CAL input may be used to perform on-line zero adjustment of the 9116’s transducers. This capability virtually eliminates sensor zero drift error and ensures the highest possible data accuracy. The CAL input may also be used for DH200 span adjustment calibrations. Span calibration of multi-range scanners may also utilize the CAL input ports if the highest applied pressure does not exceed the proof pressure rating of any installed transducer.

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