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OptoNews: Choosing I/O modules for temperature monitoring

Posted by Jean Femia on Jun 17, 2015, 4:31:00 PM

Solutions for temperature monitoringDo you monitor temperatures?

A lot of control engineers do, especially in fields like water treatment, refrigeration, thermoforming, refining, food processing, and energy or building management.

There are a variety of temperature sensors on the market—ICTDs, thermocouples, RTDs, thermistors, infrared sensors. Accuracy, cost, wiring complexity, and environmental conditions are some of the factors that determine which one is best for your application.

Here's a short white paper that helps you choose the type of temperature sensor you need.

Connect sensors to I/O

To connect temperature sensors to your system, you also have good choices in SNAP I/O analog input modules.

Each module has 2, 4, or 8 channels. Each channel can be individually configured. The higher the density, the lower the per-channel cost.

  • For ICTDs, the SNAP-AICTD-8 is designed for energy-management applications like refrigeration and HVAC. It gives you 8 channels of ICTD input.
  • For thermocouples or millivolt inputs, some modules like the 4-channel SNAP-AITM-4i have channel-to-channel isolation so you don’t need isolated probes.
  • Also for thermocouples, the SNAP-AITM-8 offers 8 channels of temperature input from a variety of standard type B, C, D, E, G, J, K, N, R, S or T thermocouples. This module saves space in molding machines and test stands.
  • For RTDs, 2-channel SNAP-AIRTD modules report temperatures from platinum or copper RTDs.
  • For thermistors, the 8-channel SNAP-AIR400K-8 offers auto-ranging and a variety of fixed ranges from 0-500 ohms up to 0-400 K ohms. Temperature is calculated automatically.

(By the way, did you see Ben’s blog post on monitoring temperatures in a water heater? He measured three states with one thermocouple input—without even knowing the thermocouple type!)

Use your brain

The real key to easier temperature monitoring, though, is the SNAP PAC brain. The brain automatically performs calculations at the I/O level that would otherwise take up controller resources. You don't even have to program these functions:

  • Measurement-unit-to-temperature conversion
  • Cold junction compensation 
  • Thermocouple linearization

The brain also has PID loop control built in: up to 96 PID loops per brain can run at the local level. That means your loop continues to work even if communication to the controller is lost.

So if you're monitoring temperatures for processes, environmental conditions, safety, or facility or energy management, be sure to take a look at SNAP I/O.

Here's the I/O Solutions for Temperature Monitoring white paper to get you started.

Read the white paper


OptoNews June 17, 2015 - Read more in this issue:

Topics: Energy management, Process control, Food & beverage, Water & wastewater, Machine builder, optonews, OEM, Integrators, OptoNews 2015-06-17

Written by Jean Femia

Jean Femia writes about technical subjects and has focused on automation and control systems for more than 15 years. She likes learning about technology and taking corners in her Honda S2000.
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