Arroyo Instruments ComboSource 6300 Series, Руководство пользователя

Страница: 51 / 60

6300 Series ComboSource User’s Manual · Page 51
instrument. For example, if you want to calibrate the laser current to within
0.1mA, then your meter would have an accuracy of 0.025mA or better. Using
lower accuracy meters could actually degrade the accuracy of the instrument
rather than improving it.
Considerations for Calibrating the Laser Current
For current calibration, more meters have poor current measurement
performance. A better approach is to measure the voltage across a known
resistor value. However, this introduces two measurement errors: the
measurement error of the resistance of the current sense resistor, and the
measurement error of the voltage across the current sense resistor, so both
much be considered when determining the overall accuracy of your
measurement system.
Considerations for Calibrating the TEC Sensors
For calibration of resistance sensors (thermistor and RTD), it is best to use a
selection of precisely measured fixed resistors, then connect them to the sensor
input on the instrument.
For LM335, the sensor is biased with a 1mA current source, so using an
appropriately ranged fixed resistor (2k
Ω to 4k Ω ) will generate a voltage in the
operating range of the sensor which can be measured by your meter.
For AD590 calibration, the sensor is biased with a ~4.5V source. Like the
LM335, you can use a precisely known fixed resistor to create a known amount
of current flowing through the sensor. By using the I = V / R calculation, you can
determine the amount of current flowing through the resistor by measuring the
voltage across the resistor.