This document describes the SLC™ 500 4-Channel Analog I/O Modules, which include Catalog Numbers 1746-NI4, 1746-NIO4I, 1746-NIO4V, 1746-NO4I, and 1746-NO4V. These modules are designed for use in SLC 500 control systems, enabling the representation of numerical quantities through continuous physical variables. They are suitable for applications involving the design, installation, programming, or troubleshooting of control systems.
Function Description
The analog modules convert current and voltage signals into 16-bit integer values for input, and convert 16-bit integer values from the output image to voltage or current signals for output.
- 1746-NI4 Analog Input Module: This module features four analog input channels. Each channel can be user-selected for either voltage or current input, making it versatile for various monitoring and controlling applications. The input channels are addressed as single words in the input image table (I:e.0 through I:e.3 for channels 0-3).
- 1746-NIO4I and NIO4V Analog Combination Modules: These modules offer a combination of two input and two output channels within a single slot.
- 1746-NIO4I: Provides two current or voltage inputs (user-selectable per channel) and two current outputs. Input channels are addressed as I:e.0 and I:e.1, and output channels as O:e.0 and O:e.1.
- 1746-NIO4V: Provides two current or voltage inputs (user-selectable per channel) and two voltage outputs. Input channels are addressed as I:e.0 and I:e.1, and output channels as O:e.0 and O:e.1.
- 1746-NO4I and NO4V Analog Output Modules: These modules provide four analog output channels.
- 1746-NO4I: Features four current outputs. Output channels are addressed as O:e.0 through O:e.3 for channels 0-3.
- 1746-NO4V: Features four voltage outputs. Output channels are addressed as O:e.0 through O:e.3 for channels 0-3.
All analog commons (ANL COM) are internally connected within the module but are not connected to earth ground. The modules do not supply loop power for input devices; users must provide appropriate loop power for loop-powered input devices.
Important Technical Specifications
General Specifications (for NI4, NIO4I, NIO4V, NO4I, and NO4V):
- SLC Communication Format: 16 Bit Two’s Complement Binary
- Field Wiring to Backplane Isolation: 500V dc
- Update Time: 512 µs for all channels in parallel
- Recommended Cable: Shielded Belden #8761
- Maximum Wire Size: #14 AWG (maximum)
- Terminal Block: Removable
- Location: 1746 chassis
- Calibration: Factory Calibrated (Refer to calibration procedure, pg. D-2)
- Noise Immunity: NEMA Standard ICS 2-230
- Operating Temperature: 0° to +60° C (+32° to +140° F)
- Storage Temperature: -40° to +85° C (-40° to +185° F)
- Relative Humidity: 5 to 95% (non–condensing)
Backplane Current Draw (Max.):
| Catalog Number |
5V (max.) |
24V (max.) |
External 24V dc Power Supply Tolerances |
| 1746-NI4 |
35 mA |
85 mA |
NA |
| 1746-NIO4I |
55 mA |
145 mA |
NA |
| 1746-NIO4V |
55 mA |
115 mA |
NA |
| 1746-NO4I |
55 mA |
195 mA |
24 ±10% at 195 mA max. (21.6 to 26.4V dc)(1) |
| 1746-NO4V |
55 mA |
145 mA |
24 ±10% at 145 mA max. (21.6 to 26.4V dc)(1) |
(1) Required for some applications if SLC 24V power is not readily available.
General Analog Input Specifications (for NI4, NIO4I, and NIO4V):
- Converter Resolution: 16 bit
- Repeatability: ±1 LSB
- Location of LSB in I/O image word: 0000 0000 0000 0001
- Non–linearity: 0.01%
- Common Mode Voltage Range: -20 to +20 volts
- Common Mode Rejection at 0 to 10 Hz (min.): 50 dB
- Common Mode Rejection at 60 Hz (min.): 105 dB
- Normal Mode Rejection at 60 Hz (min.): 55 dB
- Channel Bandwidth: 10 Hz
- Step Response: 60 ms at 95%
- Conversion Method: Delta–Sigma Modulation
- Impedance to ANL COM: 380K ohms (Series B and greater), 500K Ohms (Series A)
- Impedance channel to channel: 760K ohms (Series B and greater), 500K Ohms (Series A)
Current-Loop Input Specifications (for NI4, NIO4I, and NIO4V):
- Input Range (Normal Operation): -20 to +20 mA
- Absolute Maximum Input Current: -30 to +30 mA
- Absolute Maximum Input Voltage: ±7.5V dc or 7.5V ac RMS
- Current Input Coding: -20 to +20 mA corresponds to -16,384 to +16,384
- Input Impedance: 250 Ohms
- Resolution: 1.22070 µA per LSB
- Full Scale: 20 mA
- Overall Accuracy at +25° C (77° F) (max.): ±0.365% of full scale
- Overall Accuracy at 0° to +60° C (32° to 140° F) (max.): ±0.642% of full scale
- Overall Accuracy Drift (max.): +79 ppm/5 C of full scale
- Gain Error at +25° C (77° F) (max.): +0.323%
- Gain Error at 0° to +60° C (32° to 140° F) (max.): ±0.556%
- Gain Error Drift (max.): ±67ppm/° C
- Offset Error at +25° C (77° F) (max.): ±7 LSB
- Offset Error at 0° to +60° C (32° to 140° F) (max.): ±14 LSB
- Offset Error Drift (max.): ±0.20 LSB/° C
Voltage Input Specifications (for NI4, NIO4I, and NIO4V):
- Input Range: -10 to +10V dc - 1 LSB
- Voltage Input Coding: -10 to +10V dc - 1 LSB corresponds to -32,768 to +32,767
- Input Impedance: 760K ohms (Series B and greater), 1M ohms (Series A)
- Resolution: 305.176 µV per LSB
- Full Scale: 10V dc
- Overall Accuracy at +25° C (77° F) (max.): ±0.284% of full scale
- Overall Accuracy at 0° to +60° C (32° to 140° F) (max.): ±0.504% of full scale
- Overall Accuracy Drift (max.): ±63 ppm/° C of full scale
- Gain Error at +25° C (77° F) (max.): ±0.263%
- Gain Error at 0° to +60° C (32° to 140° F) (max.): ±0.461%
- Gain Error Drift (max.): ±57 ppm/° C
- Offset Error at +25° C (77° F) (max.): ±7 LSB
- Offset Error at 0° to +60° C (32° to 140° F) (max.): ±14 LSB
- Offset Error Drift (max.): ±0.20 LSB/° C
- Overvoltage Protection (max. across IN+ to IN- terminals): either 220V ac RMS continuously or 220V dc continuously
Current Output Specifications (for NIO4I and NO4I):
- Converter Resolution: 14 bit
- Location of LSB in I/O image word: 0000 0000 0000 01XX
- Non–linearity: 0.05%
- Conversion Method: R-2R Ladder
- Step Response: 2.5 ms (at 95%)
- Load Range: 0 to 500 Ohms
- Maximum Load Reactance: 100 µH
- Current Output Coding: 0 to +21 mA - 1 LSB corresponds to 0 to +32764
- Output Range (Normal): 0 to +20 mA
- Overrange Capability: 5% (0 to +21 mA - 1 LSB)
- Resolution: 2.56348 µA per LSB
- Full Scale: 21 mA
- Overall Accuracy at +25° C (77° F) (max.): ±0.298% of full scale
- Overall Accuracy at 0° to +60° C (32° to 140° F) (max.): ±0.541% of full scale
- Overall Accuracy Drift (max.): ±70 ppm/° C of full scale
- Gain Error at +25° C (77° F) (max.): ±0.298%
- Gain Error at 0° to +60° C (32° to 140° F) (max.): ±0.516%
- Gain Error Drift (max.): ±62 ppm/° C
- Offset Error at +25° C (77° F) (max.): ±10 LSB
- Offset Error at 0° to +60° C (32° to 140° F) (max.): ±12 LSB
- Offset Error Drift (max.): ±0.06 LSB/° C
Voltage Output Specifications (for NIO4V and NO4V):
- Converter Resolution: 14 bit
- Location of LSB in I/O image word: 0000 0000 0000 01XX
- Non–linearity: 0.05%
- Conversion Method: R-2R Ladder
- Step Response: 2.5 ms (at 95%)
- Load Range: 1K to ∞ Ohms
- Maximum Load Current: 10 mA
- Maximum Load Reactance: 1 µF
- Voltage Output Coding: -10 to +10V dc - 1 LSB corresponds to -32,768 to +32,764
- Output Range (Normal): -10 to +10 volts - 1 LSB
- Resolution: 1.22070 mV per LSB
- Full Scale: 10V dc
- Overall Accuracy at +25° C (77° F) (max.): ±0.208% of full scale
- Overall Accuracy at 0° to +60° C (32° to 140° F) (max.): ±0.384% of full scale
- Overall Accuracy Drift (max.): ±54 ppm/° C of full scale
- Gain Error at +25° C (77° F) (max.): ±0.208%
- Gain Error at 0° to +60° C (32° to 140° F) (max.): ±0.374%
- Gain Error Drift (max.): ±47 ppm/° C
- Offset Error at +25° C (77° F) (max.): ±9 LSB
- Offset Error at 0° to +60° C (32° to 140° F) (max.): ±11 LSB
- Offset Error Drift (max.): ±0.05 LSB/° C
Usage Features
Installation and Configuration:
- DIP Switches: NI4, NIO4I, and NIO4V modules feature user-selectable DIP switches to configure input channels for either current or voltage. NO4I and NO4V modules have an external 24V dc power switch (SW1) to select between an external power source or the backplane for power.
- Slot Selection: Position the module away from AC or high-voltage DC modules, in the chassis closest to the bottom of the enclosure, and away from the chassis power supply (if modular).
- Wiring: Use shielded communication cable (Belden™ 8761) with the shortest possible length. Connect only one end of the cable shield to earth ground. Analog commons are internally connected and channels are not isolated from each other. The module does not provide power for analog inputs; use a power supply matching transmitter specifications.
- Module ID Codes: When configuring the module in SLC 500 programming software, enter the appropriate Module ID Code (e.g., 4401 for 1746-NI4, 3201 for 1746-NIO4I, 3202 for 1746-NIO4V, 5401 for 1746-NO4I, 5402 for 1746-NO4V).
Operation and Programming:
- Data Update: Analog input and output data are updated by the processor once per scan (typically 10 milliseconds for a 1K program). Immediate Input/Output instructions can update 16 bits (1 analog channel) in 1 millisecond.
- Monitoring: Data can be monitored in decimal or binary radix using programming software. Binary data is viewed in two’s complement for negative values.
- Input Channel Filtering: Modules incorporate a 6-pole Gaussian digital filter to reject high-frequency noise while passing normal input signal variations. The filter has a sharp cut-off at 10 Hz (under 3 dB attenuation). Noise at 50/60 Hz is attenuated by over 55 dB. Differential inputs further reduce noise by over 105 dB (60 Hz common mode rejection). The input value settles to within 95% of the final value in 60 milliseconds.
- Safe State for Outputs: When the SLC 500 system is not in RUN mode (FAULT, PROGRAM, or TEST mode), analog outputs are automatically forced to 0 Volts or 0 mA.
- Retentive Programming Option: This option allows analog data in Input and Output Image tables to be retained during RUN-PROGRAM-RUN mode transitions or power cycles. Retained data is transferred to the module when power is reapplied. If a fault occurs, analog outputs reset to zero, but data in the Output Image table is retained.
- Input Out-of-Range Detection: Modules do not provide an inherent out-of-range signal. Users can program the processor to implement this function using compare instructions or the Limit Test (LIM) instruction (for SLC 5/02 and higher processors).
- Slot Disable Response: When a slot containing an analog module is disabled, the module continues to update input values, but the processor does not read them; inputs remain in their last state. For outputs, the module holds its outputs in their last state, and data from the processor image table is not transferred.
Programming Examples:
The manual provides examples for:
- Addressing, Out-of-Range Detection, and Scaling of Analog Inputs: Demonstrates scaling input values into engineering units (e.g., temperature in Celsius) and setting flags for out-of-range conditions. Examples use standard math, Scale (SCL) instruction (SLC 5/02+), and Scale with Parameters (SCP) instruction (SLC 5/03 OS302+, SLC 5/04 OS401+, SLC 5/05).
- Addressing and Scaling Outputs: Shows how to scale output values (e.g., valve opening percentage to current signal) using standard math and SCP instruction.
- Scaling Offsets when > 32,767 or < -32,768: Addresses situations where offset values exceed standard integer limits by shifting the linear relationship.
- Scaling and Range Checking of Analog Inputs and Outputs: Combines input scaling and range checking with output scaling.
Maintenance Features
Preventative Maintenance:
- Environmental Protection: Protect printed circuit boards from dirt, oil, moisture, and airborne contaminants by installing the SLC 500 system in a suitable enclosure. Keep the enclosure clean and closed.
- Connection Inspection: Regularly inspect terminal connections for tightness to prevent improper functioning or component damage.
- Calibration: Software calibration can be performed to increase accuracy by reducing offset and gain errors. The recommended calibration period is once every 6 months, or every 3-4 months if operating temperatures vary widely.
Safety Considerations When Troubleshooting:
- Power Disconnection: Always disconnect power from the chassis and all wired devices before installing, removing, or wiring modules.
- Electrostatic Discharge (ESD): Avoid exposing analog modules to electrostatic charges, which can destroy circuitry.
- Machine Motion: During system checkout, disconnect prime movers (motion devices) to prevent unexpected machine motion. Never reach into a machine to actuate a device.
- Module LED: The red LED on the analog module indicates 24V dc power. If it's not illuminated, check the power supply, chassis slot, and external power switch (for NO4I/NO4V).
- Input Configuration: Ensure DIP switches for voltage/current mode are set correctly. Connecting a voltage source to a current-configured channel can cause improper operation or damage.
- Grounding: Ensure the cable shield is properly grounded at one end (chassis mounting tab for input, analog load for output). Do not connect the foil shield or drain wire to the analog module terminal block.
- Program Integrity: If program alteration is suspected (due to environmental conditions, EMI, improper grounding, or tampering), check the program against a previously saved version.
- Safety Circuits: Hard-wired safety circuits (e.g., limit switches, stop buttons) must always be connected to the master control relay and should never be altered.
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