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Thermocouple Selection Guide |
| The Series 90-30 PLC offers the finest integration of PLC and thermocouple temperature
sensors in the industrial market today. Unlike other PLC's, which typically feature
one thermocouple input module or none at all, the Series 90-30 PLC features ten.
This provides the PLC user with unmatched flexibility to maximize price/performance
to each application. The table below list each Horner Electric thermocouple module and its corresponding features and specifications. |
Thermocouple Input Selection Guide: HE693THMxxx |
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| 409 | 449 | 665 | 666 | 668 | 809 | 884 | 888 | 889 | 166 | |
| 12V | 1000V | 12V | 35V | 12V | ||||||
| Open Circuit Detection | x | x | x | x | x | x | x | x | x | x |
| Open Circuit Alarms | x | x | x | x | x | x | x | x | ||
| Upscale/Downscale Break Select | x | x | x | x | x | |||||
| Alarm Setpoints | x | x | x | x | x | |||||
| Highest Resolution | 0.5°C | 0.1°C | 0.5°C | 0.1°C | 0.5°C | |||||
| 50Hz Filter | x | |||||||||
| 60Hz Filter | x | x | ||||||||
| External Cold Junction Compensation | x | x | x | x | x | |||||
| Maximum Safe Input Level.
This is the absolute voltage level (relative to PLC ground) which the module can
withstand on its input channels without damage. Extremely high safe levels are
required in applications where the thermocouple voltage is floating far above ground, or
where a failure condition can cause high voltage to be directly applied to thermocouple
wiring. Open Circuit Detection. This feature is sometimes called "upscale break". All Horner Electric thermocouple input modules have the ability to detect an open circuit condition on an input channel. Many thermocouple sensor failures are characterized by an open circuit condition. When a module detects an open circuit condition, typically it causes the analog input value for that channel to go to maximum. In a heating application, this is ideal because a suddenly high temperature value should cause the control logic to shut off the heating apparatus, usually the safer condition. Upscale/Downscale Break Select. The module with this feature can selectively go to maximum or minimum upon detecting an open circuit condition on the input channel. This could be important in a cooling application, when a minimum value is desired upon a break condition. In this case, a low value in the input channel should cause the control logic to shut off the cooling apparatus, usually the safer condition. Open Circuit Alarms. A module with this feature has a digital input bit (%I) assigned to each channel which will activate upon detection of an open circuit condition. This bit energization is in addition to the analog input value going to maximum (or minimum). Alarm Setpoints. A module with this feature has an analog output register (%AG) and a digital input point (%I) assigned to each channel. The user logic sets the analog output register to a decimal value used as a setpoint. When the channel's input value is less than the setpoint, its digital input is off. When the channel's input value is equal to or greater than the setpoint, the digital input is energized. Resolution. Horner Electric thermocouple input modules support either 0.5° (standard) or 0.1° (high) resolution. Both °C and °F units are supported by all models. 50Hz Filter. In applications with a high degree of 50Hz noise induced directly onto the thermocouple sensor, this feature will provide a stable input value. Otherwise, wild fluctuations in input values can occur in these applications. 60Hz Filter. This filter performs identically to the 50Hz version. It provides a stable input value in applications with a high degree of 60Hz noise. External Cold Junction Compensation. The terminal blocks used on Series 90-30 I/O modules were not designed for optimum thermal characteristics. Modules with the ability to use external cold junction compensation can take advantage of specially constructed terminal blocks designed for consistent thermal characteristics. This improves accuracy in some applications.
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