pico Technology USB DrDAQ, Руководство пользователя

Страница: 36 / 44

Product information 32
Copyright © 2013 Pico Technology Ltd. All rights reserved. usbdrdaq.en r4
ScopeRange=1.25V
This is used when scaling the scope channel. It specifies the range of the scope
channel that should be used. Possible values are 10 V, 5 V, 2.5 V, and 1.25 V.
NoOfPoints=32
This is the number of table lookup points.
Raw1=2.385
Raw value for the first point in the look up table. The value is in V (volts) and
should not be greater than 2.500 V, except when using the scope channel when the
minimum and maximum values correspond to the selected range.
Scaled1=-30
Scaled value for the first point in the look up table. The units are specified by the
units parameter.
2.10.6 Calibration
You can adjust the calibration of the USB DrDAQ and its sensors using the Scaling
Files . However, all input channels of a USB DrDAQ are calibrated during
manufacture.
Calibration involves measuring a known value (such as the temperature of boiling
water, or the resistance of a known resistor, or the values shown by a calibrated
sensor) then converting these values into the units you need.
Linear
Single-Point Calibration
When calibrating a sensor with a linear response curve it may only be necessary to
perform a
Single-Point Calibration . This only occurs in one circumstance:
One pair of values is known - for example on the USB DrDAQ oxygen sensor. The
sensor is known to output 0 mV at 0% oxygen content. Therefore we only need to find
one other pair of values. All we are doing here is changing the gradient of the
response curve. See the
Oxygen Sensor description for a full example.
Two-Point Calibration
A two-point calibration should always be carried out if possible, since it is the most
accurate calibration method for a sensor with a linear response curve.
30
22