1746-NI4 — SLC 500 4-Channel High-Resolution Analog Input Module

The 1746-NI4 is a 4-channel analog input module for the SLC 500 modular chassis, with each channel independently selectable for voltage (±10V DC) or current (±20 mA) input via onboard DIP switches. It uses 16-bit sigma-delta conversion for high measurement resolution, occupying a single chassis slot and connecting field instruments through a removable terminal block.

Specifications

Parameter	Value
Part Number	1746-NI4
Platform	SLC 500 (1746 series)
Input Channels	4 (differential, voltage/current selectable per channel)
Voltage Range	±10V DC
Current Range	±20 mA (±30 mA max)
Resolution	16-bit
Update Time	512 μs (all channels in parallel)
Current Input Impedance	250 Ω
Voltage Input Impedance	1 MΩ
Isolation	500V AC / 710V DC (backplane to field)
Backplane Current	35 mA @ 5V, 85 mA @ 24V
Operating Temperature	0°C to 60°C

Switch-Selectable Channels on a Legacy Analog Module

Before per-channel software configuration became standard on analog modules, the 1746-NI4 used onboard DIP switches to set each channel's signal type — a physical switch for channels 0 and 1, configuring voltage mode when off and current mode when on. This hardware-level selection means the module's input type is set at the panel, not through software configuration alone, which matters when troubleshooting an unexpected reading: verifying the physical switch position is a necessary step that software-configured modules don't require.

A specific caution applies given this hardware switch architecture: connecting a voltage source to a channel configured (via switch) for current input — or vice versa — can damage the module or produce incorrect readings without an obvious fault indication. Confirming switch position matches the connected field device's signal type before wiring is the standard commissioning step that prevents this.

FAQ

Q: Are the four channels individually isolated from each other?

No. The channels are differential but not individually isolated from one another — field devices connected to this module should share a common ground reference to avoid measurement errors.

Q: Can a 4–20 mA transmitter be wired directly to this module?

Yes, provided the corresponding channel's DIP switch is set to current mode. The module's current range covers 4–20 mA within its broader ±20 mA capability.

Q: What happens if a voltage signal is applied to a channel switched for current input?

This can cause improper module operation or damage to the input circuitry — always verify the DIP switch position matches the connected device's actual signal type before applying power to the field wiring.

Q: Does an external 24V DC power supply need to be connected to this module?

No. The 1746-NI4 draws its operating power entirely from the SLC backplane (5V and 24V rails) — no separate external power connection is required for the module itself.

1746-NI4 Brand New Original SLC 4 Point Input/Output Module 1746NI4