Measurement Computing PointScan 300 Series rev.1.0 - Manual (Page 10)

1-4 Overview 9-26-01 PointScan/300 Series Manual
Gateway Memory
All PointScan/442 gateways have nonvolatile (battery-free) memory for storing configuration data from the
I/O Toolkit utility.
Programmable gateways have battery-backed memory for storage of program variables and logged data.
The battery is a rechargeable lithium cell that is kept fresh by the power circuitry in the gateway. The
memory retention period for an unpowered gateway is at least one year at room temperature. The retention
time will be shorter at higher temperatures. The life expectancy of the lithium battery is approximately 10
years.
Calibration
All PointScan/300 Series analog I/O logic modules are factory calibrated over all supported ranges using a
regularly maintained set of standards. Factory calibration data is stored in permanent memory in the logic
module, and cannot be altered. User recalibration may be performed, but is necessary only if inaccuracy in
your field device is observed, or if any of the 100 ohm input shunts are replaced with low tolerance
resistors.
Each analog channel has span and offset calibration settings. Span is the "range" or "gain" of the channel.
Offset is the "zero" setting. Each reported analog I/O value is the product of the factory calibration value
times the user calibration value. The user calibration value is defined as:
(user span value * raw value) + user offset
The user span is a unity value (1) by default. The user offset is zero by default.
Note: All factory and user calibrations are performed in software. There are no adjustment
potentiometers inside the logic modules.
User calibrations are performed using the IO Toolkit utility. Refer to the IO Toolkit on-line help system for
information on calibrating PointScan/300 Series analog I/O.