Section 6: Maintenance; Calibration; Full Calibrations; Field Calibrations - Scanivalve DSA3217-PTP Series Operation And Service Manual

Section 6: Maintenance

SECTION 6: MAINTENANCE

Calibration

The DSA3200-PTP series uses a well proven, very stable,
temperature compensated TO-8 style piezoelectric pressure
sensor. The use of this series of sensors, along with the
ability to perform frequent, online zero offset calibrations
allows the DSA-PTP to hold published accuracy for up to
6 months. Scanivalve recommend validating the DSA-PTP
with a high-accuracy pressure standard on 6 month inter-
vals and recalibrating the unit as required.
Every DSA-PTP module is calibrated from the factory over
a series of 9 temperatures between 0°C and 72°C. At each
temperature, 9 pressures are applied. This calibration cre-
ates a matrix of discrete temperatures and pressures, called
Master Calibration Coefficients. The DSA-PTP then inter-
polates between each of these points to create a complete
matrix of "calculated" coefficients.
When recalibrating a DSA-PTP module, there are three
types of calibrations that can be performed:

Full Calibrations

A full calibration deletes all calibration coefficients and
re-applies known pressures over a series of temperatures.
This duplicated exactly what is done at the factory during
the module's original manufacture and calibration. This
calibration requires an environmental chamber capable of
reaching the entire 0°C and 72°C range and a suitable pres-
sure standard. It is recommended that for a full calibration
the module be returned to Scanivalve or a certified Scani-
valve Representative.

Field Calibrations

As an alternative to Full Calibrations, Scanivalve offers a
free program called "PressCal" that allows any metrology
lab with a suitable pressure standard to perform a "Field
Calibration." During a field calibration, a series of pressures
are applied to the module at a single temperature. The
temperature of the module does not have to be controlled
to a specific temperature. PressCal calculates a new set
of coefficients for that given temperature, then applies a
correction to the pressure coefficients across all tempera-
tures. This technique is suitable for maintaining modules
long term and has been proven to be just as good as a new
full calibration when done properly. More information
on PressCal can be found on the Scanivalve website or by
contacting Scanivalve.

Zero Offset Calibration

In all piezoelectric pressure sensors, zero drift is the single
largest contributor to long term errors. Because of this, all
DSA3217-PTP and 3218-PTP modules have internal calibra-
tion valves and a software command (CALZ) that allow for
a zero offset calibration to be performed easily and fre-
quently. More information on the Zero Offset Correction
calibrations can be found in "Zero Offset Calibration" on
page 13, and information on the CALB and CALZ com-
mands can be found in "Calibrate Barometric Pressure" on
page 21 and "Calibrate Zero" on page 22 respectively.
62
62
DSA3200-PTP