National Instruments 6527 Isolation Voltages, Optically Isolated Inputs

Chapter3 MakingSignal Connections

©NationalInstruments Corporation 3-7 6527User Manual

Isolation Voltages

The positive and negative (DIG+ and DIG–) terminals of each channel

are isolated from the other input and output channels, from the +5 V and

GNDpins, and from the computer power supply. Isolation barriers provide

isolationup to 60 VDC or 30 VAC(42 V peak) between any two terminals,

exceptbetween the two terminals making up a single digital I/O channel.

Do notexceed 60 VDC or 30 VAC between any two terminals of the

6527 device,including:

•anytwo digital I/O (DIG +or DIG–) lines of separate channels

•anyDIG+ or D IG–lineandtheGNDor+5Vlines

•the DIG+ line and the DIG–line of any output channel

Do notexceed 28 VDC or apply any negative or AC voltage between the

DIG+an d DIG–terminals of any input channel.

Warning Donot exceed the isolation voltage limits. Exceeding the voltage limits can lead

to injury.National Instruments is not liable for any damage resulting from signal

connectionsthat exceed these limits.

Optically Isolated Inputs

On a 6527 device, I/O connector pins 1 through 48, shown in Figure 3-1,

represent the optically isolated input signal pins.

The optically-isolated inputs of a 6527 device contain a light-emitting

diode (LED), a resistor for current limiting, and digital filtering and

change-detection circuitry.The 6527boards offer 24 channels of isolated

digital input. Each channel has its own positive and negative terminals.

Always apply the higher voltage, if any, to the positive terminal. The

maximuminput voltage (VIN) on these channels is +28 VDC.

Caution Neverapply a voltage to the positive (DIG+) terminal of any input channel that

is lowerthan the voltage on the channel’snegative(DIG–)terminal. National Instruments

is not liable for anydam age resulting from incorrect signal connection.