Crystal nVision Reference Recorder Operation Manual page 41

Although we prefer that you return the nVision to Crystal Engineering for calibration, ordinary
recertification and/or adjustments may be performed by any qualified personnel with appropri-
ate training and equipment. The following instructions are ONLY intended for such qualified
personnel with appropriate test equipment. We recommend that the calibration standards used
have a minimum rated accuracy of 0.008% of reading, or equivalent in terms of percent of full
scale. This level of accuracy requires the use of piston (deadweight) gauges or very high perfor-
mance pressure controllers.
There are no internal potentiometers. The nVision contains a "span" factor
(userspan), set to approximately 1 (as shipped from the factory). As components age this may
need to be changed to a value slightly higher or lower, to slightly increase or decrease all read-
ings. This adjustment can be made with a computer through CrystalControl.
Calibration for Pressure Modules (PM): "Zero" the nVision, then record
displayed pressure for two or more pressure points. Determine if the nVision would benefit
from an overall increase or decrease of the indicated pressures. Adjust userspan accordingly
and validate results.
Calibration for Current, Voltage & Switch Test Module (MA20): The MA20
can be calibrated through the use of the span factor (userspan) and the Offset for the current
and voltage modes. Record displayed current or voltage for two or more points. Determine
if the nVision would benefit from an overal increase or decrease of the indicated reading and
modify using the userspan and offset feature of CrystalControl.
To calibrate the Switch Test, use the CrystalControl Calibration Wizard. Install your red and black
test leads into the Switch Test locations as shown in the wizard. Ensure that the leads are not
connected together forming a closed circuit. After pressing 'start' the application will survey the
circuit in the open state. When prompted by "Waiting for switch to close..., " connect the red and
black test leads together creating a closed circuit. The application will survey the circuit in the
closed state. After this process the switch test will be fully functional and ready to use.
Calibration for Temperature Modules (RTD100): The RTD sensor can be
calibrated through the use of the span factor (userspan) and the Base Resistance (Ro) at 0ºC. Re-
cord displayed temperature for two or more temperature points. Determine if the nVision would
benefit from an overall increase or decrease of the indicated temperatures and modify using the
userspan feature in CrystalControl. It is also possible to modify the RTD sensor resistance reading
at 0ºC to a custom value other than the default value of 100 Ω using the Base Resistance (Ro) at
0ºC in CrystalControl. Note, however, that the Ro offset will affect all RTDs used with the nVision
and should be used with care.
nVision Operation Manual • Page 35