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$320.00 (USA and Canada only)

Availability: In stock
SNAP 4-Ch Analog Thermistor Input Module

Production Specification

The SNAP-AIR40K-4 provides four channels of analog-to-digital conversion, ideal for thermistors used in HVAC applications or for reading the resistance of potentiometer input. Default range is 0-40 K Ohms; the module can also be configured for 0-20 K, 0-10 K, or 0-5 K Ohms. Resistance probes must be isolated from each other.

Part of the SNAP PAC System, the module mounts on a SNAP PAC rack with a SNAP PAC brain or rack-mounted controller. Analog, digital, and serial I/O modules can all be on the same rack. Such an I/O unit is also well suited for PC-based control or for use as intelligent remote I/O for an Allen-Bradley Logix PLC system, such as ControlLogix, MicroLogix, or CompactLogix.

Compatibility: This module can be used with SNAP PAC brains and R-series controllers. It can also be used with legacy SNAP Ethernet-based brains.

Also see the 8-channel SNAP-AIR400K-8, ideal for NTC thermistors as well as PTC thermistors.

Build your system in the SNAP I/O Configurator.

Input Range

0 to 40,000 Ohms
0 to 20,000 Ohms
0 to 10,000 Ohms
0 to 5,000 Ohms

Maximum Over-Range

44 K (40 K Ohms range)
22 K (20 K Ohms range)
11 K (10 K Ohms range)
5.5 K (5 K Ohms range)


1.6 Ohm @ 40 K Ohms
0.8 Ohm @ 20 K Ohms
0.4 Ohm @ 10 K Ohms
0.2 Ohm @ 5 K Ohms

Input Filtering

-3 dB @ 3.2 Hz

Data Freshness (Max)

100 (40 K Ohms)
200 (20 K Ohms)
400 (10 K Ohms)
800 (5 K Ohms)

DC Common Mode Rejec­tion

>-120 dB

AC Common Mode Rejec­tion

>-120 dB @ 60 Hz

Maximum Operating Com­mon Mode Voltage

250 V


0.1% ± 40 Ohms @ 40 K Ohms
0.1% ± 20 Ohms @ 20 K Ohms
0.1% ± 10 Ohms @ 10 K Ohms
0.1% ± 5 Ohms @ 5 K Ohms

DRIFT: Gain Temperature Coefficient

30 PPM/ °C

DRIFT: Offset Tempera­ture Coefficient

15 PPM/ °C


1500 V

Power Requirements

5 VDC (±0.15 ) @ 190 mA

Operating Temperature

-20 °C to 70 °C

Storage Temperature

-40 °C to 85 °C


5-95%, non-condensing

Wire size

22 to 14 AWG

Torque, hold-down screws

4 in-lb (0.45 N-m)

Torque, connector screws

5.26 in-lb (0.6 N-m)

Agency Approvals




SNAP PAC System Product Guide

This document lists and describes all Opto 22 SNAP PAC System part numbers, including PAC Project software, SNAP PAC controllers, SNAP PAC brains, and SNAP I/O modules of all kinds. SNAP PAC mounting racks and SNAP power supplies are also listed.

SNAP Analog Input Modules Data Sheet

SNAP I/O analog input modules are part of Opto 22's SNAP PAC System. This document includes descriptions, specifications, and wiring and dimensional diagrams for the following analog input modules:

For analog modules with channel-to-channel isolation, see Form 1182, the SNAP Isolated Analog Input Modules Data Sheet.

I/O Solutions for Temperature Monitoring (Chinese)

This document is written in Chinese.

This white paper describes various temperature sensors such as RTDs, thermocouples, ICTDs, thermistors, and infrared sensors, and the Opto 22 solutions for using them.

Primer: I/O Solutions for Temperature Monitoring

This primer describes various temperature sensors such as RTDs, thermocouples, ICTDs, thermistors, and infrared sensors, and the Opto 22 solutions for using them.

Opto 22 RoHS 3 Statement of Compliance - Restriction of Hazardous Substances

This document is a statement of compliance with the EU Directive 2015/863/EU, Restriction of Hazardous Substances (RoHS 3). This document lists Opto 22 products that comply with the substance restrictions of the RoHS 3 directive.

FM Approval Document

This document lists all Opto 22 part numbers that have Factory Mutual (FM) approval.

UL Approval Document

This document lists all Opto 22 part numbers that have the Underwriters Laboratory (UL) approval.

CE Declaration: Low Voltage

This document is the Manufacturer's Declaration for the listed products as mentioned in the attachment - to which this confirmation refers - that they are in accordance with the mentioned European, international and/or national standards and regulations.

CAD Drawing: SNAP I/O Module

This CAD file includes drawings that apply to most SNAP analog and digital I/O modules.

Scaling and Linearization Example

A example strategy written in PAC Control Basic R8.2f that demonstrates how to scale and linearize values. This example strategy uses subroutines to perform most calculations.

Before you download, read the Legal Agreement.

Video: SNAP PAC System Overview

This overview describes the four integrated components of the SNAP PAC system: software, controllers, brains and I/O. This hardware and software system is designed for industrial control, remote monitoring and data acquisition.

Video: Securing SNAP Module

A quick overview on securing a SNAP Module to a SNAP rack.

Video: Removing a SNAP Module

A quick overview on removing a SNAP module.

Video: I/O Solutions for Temperature Monitoring

A quick overview on I/O Solutions for temperature monitoring.

Accuracy vs Resolution

What's the difference between accuracy and resolution in analog I/O specifications? Try your own specs in the calculator.