AI843 Thermocouple/mV Input Module

Description

The AI843 Thermocouple/mV Input Module is part of the S800 I/O series. It provides 8 differential input channels for thermocouple/mV measurements. Measurement ranges configurable per channel are: -30 mV to +75 mV linear, or TC Types B, C, E, J, K, L, N, R, S, T, and U.

A separate Pt100 channel is used for “Cold Junction” (ambient) temperature measurements, thus serving as the CJ-channel for channels 1 to 8. See Figure 44, Figure 45, and Figure 46 for the connection of reference resistance and Pt100 sensor. The junction temperature can be measured locally on the MTU's screw terminals or on a connection unit distant from the device. Alternatively, a fixed junction temperature for the module may be set by the user (as a parameter) or a junction temperature set by the application.

Each input channel can measure an mV type of signal source (thermocouple or linear) and may be grounded or ungrounded. Full self-calibration is achieved by means of 0V and 30 mV references, which are regularly updated. On each channel, there is a Fault (Red) LED that indicates channel error.

Features

• 8 differential input channels for thermocouple/mV.
• Single or redundant operation.
• A separate channel is used as CJ-channel (4-wire Pt100 RTD).
• Supports thermocouple types: B, C, E, J, K, L, N, R, S, T, and U.
• 16-bit resolution (A/D converter).
• Inputs are monitored for wire-break open-circuit.

Three different types of MTUs can be used:

• Single applications: TU830 Extended MTU enables three-wire connection to the devices without additional terminals.
• Redundant applications: TU842 for horizontal mounting and TU843 for vertical mounting can be used.

Shielded field cables are required for process connections.

Technical Data

General Specifications at 25°C

• Number of channels: 8 (Differential)
• Type of input: -30 mV to 75 mV linear, or TC types B, C, E, J, K, L, N, R, S, T, and U
• Input impedance: > 1 MΩ
• CJ-temperature measurement reference: 4-wire connected IEC-751/Pt100 RTD, TY820 can be used
• Maximum field cable length: 600 meters (656 yd.) or max. 500 Ω
• CMV between channels, max.: 5 V d.c.
• CMRR, 50 Hz, 60 Hz: 100 dB
• NMRR, 50 Hz, 60 Hz: >40 dB
• Resolution (A/D converter): 16 bits
• Error: <0.1%
• Temperature drift:
  • Typical: 10 ppm/°C
  • Max: 25 ppm/°C
• Filter, analog (1st order Low-pass): 1.1 kHz
• Filter (integration): 50 Hz or 60 Hz
• Update cycle time, max.:
  • 320 ms + $n \times 80$ ms at 50 Hz
  • 267 ms + $n \times 67$ ms at 60 Hz (n = active channels)
• Supervision:
  • Module error: If reference channels outside limits, power supply low
  • Channel error: If open-circuit, out of range <-40°C (-40°F) and >100°C (212°F) (only Cold Junction channel)
  • Linear: None
• Current consumption 24 V (Modulebus): 50 mA
• Current consumption 5 V (Modulebus): 60 mA
• Power dissipation: 1.5 W

Isolation

• Groupwise isolated from ground

Mounting Termination Units

• TU818
• TU830
• TU842
• TU843

MTU Keying Code

• B, A

Rated Insulation Voltage

• 50 V

Dielectric Test Voltage

• 500 V a.c.