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$600.00 (USA and Canada only)

Availability: In stock
SNAP 8-Ch Analog Resistor/thermistor Input, 400 K Ohms

Production Specification

The SNAP-AIR400K-8 module has eight channels of analog to digital conversion that convert resistance to temperature or to ohms. The module is ideal for NTC thermisters commonly used in HVAC, refrigeration, and process control applications. It may also be used with PTC thermisters in resistance sensing applications.

The SNAP-AIR400K-8 reads variable resistance type transducers, and it has 12 resistance input ranges from 500 Ohms to 400 K Ohms, plus Autorange. Range dependent resolution is from 20 milliohms to 16 Ohms. SNAP PAC brains and PAC Control provide direct temperature readings for four popular thermistors using the Steinhart-Hart equation. You may also enter custom coefficients for unsupported thermistor curves.

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. Minimum requirements: brain or controller firmware R9.3c and PAC Project R9.3002 (PAC Control R9.3b).

Also see the 4-channel SNAP-AIR40K-4.

Build your system in the SNAP PAC Configurator.

Input Ranges

400 K, 200 K, 100 K, 50 K, 40 K, 20 K, 10 K, 5 K , 4 K, 2 K, 1 K, 500 Ohms, and Autorange


16 Ohm
  8 Ohm
  4 Ohm
  2 Ohm

0 to 400 kOhms
0 to 200 kOhms
0 to 100 kOhms
0 to   50 kOhms

1.6 Ohm
0.8 Ohm
0.4 Ohm
0.2 Ohm

0 to 40 kOhms
0 to 20 kOhms
0 to 10 kOhms
0  to  5 kOhms

0.16 Ohm
0.08 Ohm
0.04 Ohm
0.02 Ohm

0 to 4 kOhms
0 to 2 kOhms
0 to 1 kOhms
0 to 500 Ohms

(Ohms @ Range)

400 Ohms @ 400 K
200 Ohms @ 200 K
100 Ohms @ 100 K
  50 Ohms @   50 K

 40 Ohms @ 40 K
 20 Ohms @ 20 K
 10 Ohms @ 10 K
   5 Ohms @   5 K

4   Ohms  @ 4 K
2   Ohms  @ 2 K
1   Ohms  @ 1 K
0.5 Ohms @ 500

Data Freshness

1.61 seconds maximum

DSP Notch Filter

20 Hz (- 3DB = 5.24 Hz)

Excitation Current Nomi­nal (Range & Load Watts Dissipation)

9uA (50 K–4.1 uW), (100 K–8.1 uW), (200 K–16 uW), (400 K–32 uW)
90uA (5 K–40 uW), (10 K–81 uW), (20 K–160 uW), (40 K–320 uW)
200uA (500 K–20 uW), (1 K–40 uW), (2 K–80 uW), (4 K–160 uW)

Autorange Step Time

1.6 seconds to next higher or lower range
>= 10 seconds for a 500 Ohms to 400 K Ohms step change

Autorange Ohms Hyster­esis

Ohms    Open  >  440K

20K      between 200K & 400K
10K      between 100K & 200K
5K        between 50K & 100K

19K      between
40K & 50K
2K        between 20K & 40K
1K        between 10K & 20K
500       between 5K & 10K

1.9K      between 4K & 5K
200       between 2K & 4K
100       between 1K & 2K
50         between 500 & 1K

DC Common Mode Rejec­tion

>-120 dB

AC Common Mode Rejec­tion

>-120 dB @ 60 Hz

Open Resistor Indicator

Channel resistance = 999,999.999 Ohms

PAC Control Reads

temperature reading or -32768 Ohms if over or under range

Maximum Operating Common Mode Voltage
(Field Term to Logic Con­nector)

500 VDC or peak VAC

Gain Tempco
Offset Tempco

30 PPM / °C
15 PPM / °C

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

Torque, hold-down screws

Not to exceed 1 in-lb (0.11 N-m)

Torque, connector screws

5.22 in-lb (0.59 N-m)

Agency Approvals




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.

UKCA Declaration of Conformity (EMC, LVD, RoHS)

This document is the Manufacturer's Declaration of Conformity for the products listed herein, in accordance with the rules, regulations and standards of the United Kingdom. The models cited have been tested to the essential requirements listed in the Standards section, and fully comply with the legislation as listed in UK Legislation section.

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.

UL Approval Document

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

No downloads are available for this product.

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: I/O Solutions for Temperature Monitoring

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