Advantech PCIE-1840, Руководство пользователя

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PCIE-1840 User Manual 18
3.3.3 PCLD-8841 Signal Connection
To ensure the accuracy of PCIE-1840 would not drift by time, periodical calibrations
are necessary to make the performance match its specification. PCIE-1840 provides
two methods for calibration, manual-calibration and self-calibration with PCLD-8841.
By manual calibration, PCIE-1840 could achieve higher accuracy but it takes more
time and is suitable for the users who require a single channel calibration. Self-cali-
bration with PCLD-8841 provides a convenient way for user to calibrate all input
ranges. Both calibrations are required to be done after ambient temperature is stable.
Twenty minutes warm-up after PCIE-1840 begins running is necessary. Doing cali-
bration periodically can ensure the accuracy is the same over time.
Figure 3.5 PCLD-8841 board diagram for Auto-calibration
3.3.3.1 Self-Calibration
Self-calibration provides a convenient way to calibrate all input ranges with the assis-
tance of PCLD-8841. Before starting self-calibration, users need to fine-tune PCLD-
8841 output to make sure the reference voltage is accuracy. Users should connect
VOUT to a high precision multi-meter, at least 6-1/2 digital meter, and tune the eight
on-board variable resistors to the dedicated voltages. The following table lists the
functions of these variable resistors.
Table 3.2: PCLD-8841 Reference Voltage Output Tunning
Variable Resistor # Dedicated Voltage (after tuning) Corresponding Calibration
VR1 9.9 V 20 Vp-p, Gain Error
VR2 4.95 V 10 Vp-p, Gain Error
VR3 1.98 V 4 Vp-p, Gain Error
VR4 0.99 V 2 Vp-p, Gain Error
VR5 0.495 V 1 Vp-p, Gain Error
VR6 0.198 V 0.4 Vp-p, Gain Error
VR7 0.099 V 0.2 Vp-p, Gain Error
VR9 0V (GND) ALL, Offset Error