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Safety
Maximum Voltage
1
Connect only the voltages that are within these limits.
RS232 Receive Signal-to-
COM (RXD, CTS, DSR,
DCD, RI)
±25 V max, Measurement
Category I
RS232 Transmit Signal-to-
COM (TX, RTS, DTR)
±13.2 V max, Measurement
Category I
V
SUP
-to-COM
±28 V max, Measurement
Category I
Measurement Category I is for measurement performed on
circuits not directly connected to the electrical distribution system
referred to as MAINS voltage. MAINS is a hazardous live
electrical supply system that powers equipment. This category is
for measurements of voltages from specially protected secondary
circuits. Such voltage measurements included signal levels,
1
The maximum voltage that can be applied or output without creating a safety
hazard.
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NI 9870 Getting Started Guide