Vibro-Meter XMC16 16-channel combustion monitoring card

XMC16 16-channel combustion monitoring card

Sensor signal conditioning

This block (see Figure5-2) acts as a signal interface and is used to:

• Acquire a signal from the connected sensor.

• Check for signal overload (independently of the OK line check).

The AMC8 card does not have the ability to power external measuring devices. Where

necessary, an external power supply must be used.

See 5.3Inputs and outputs.

5.2.2Signal routing

This block (see Figure5-2) is used only if cold-junction compensation (CJC) is required for

channels having a thermocouple connected.

The block enables a “cold junction” (CJ) temperature signal (generally obtained using an

RTD) to be routed to another channel on the card. One of two remote CJ signals can also be

selected. These come from other cards in the rack over Tacho Bus lines 7 and 8.

5.2.3Signal processing and monitoring

This block (see Figure5-2) assures the following:

1-Definition of “multi-channels”

Based on the eight single channels, four “multi-channels” can be defined. These can

group between two and eight single channels and perform various mathematical

operations on them, such as obtain the minimum, maximum or average value. The

difference between two individual channels can also be calculated.

See 5.4Multi-channel processing functions.

2-Selection of the time-domain processing function

The functions include the following: direct output (bypass), average over a period of time,

maximum value over a period of time, minimum value over a period of time.

See 5.5Time-domain processing functions.

3-Linearity compensation

Linear and non-linear sensor compensation can be applied for thermocouples and RTD

devices.

See 5.6Linearity compensation.

4-Monitoring

For single channels and “multi-channels”, the signal values (suitably processed and

compensated) are monitored and alarms generated if the thresholds are exceeded.

These alarms can be used to set relays.

Logical combinations of alarms can also be configured.

See 5.8Alarm monitoring.

5-Sensor OK Level Detection

This function monitors the OK levels for the sensor to check for hardware problems (for

example, faulty sensor or signal conditioner, or defective transmission line).

See 5.9System self-checks

Inputs and outputs

5.3.1Measurement signal inputs

The following sensor types can be used with the AMC8/IOC8T card pair:

• Thermocouples (typeE, typeJ, typeK, typeT or user defined)

• RTD devices (Pt100. Cu10. Ni120 or user defined)

• Other measurement systems such as flow rate detectors or power indicators providing a

quasi-static signal. This can be a current-based signal (typically 4to20mA, but an

extended range of 4to25mA can also be processed) or a voltage based signal

(0to10V).

RTD devices can be connected in a 2-wire, 3-wire or 4-wire arrangement.

A 50Ω measuring resistor is used for systems providing a current-based signal. The input is

protected by a self-resetting 50mA fuse.

For voltage-based signals, only unipolar signals can be processed. Negative signals can be

measured simply by reversing the polarity of the input wires.

Hardware associated with the sensors such as power supplies, signal conditioners, optional

safety barriers or galvanic separations are not implemented within the MPS rack, but

externally.

NOTE: See 10Configuration of AMC8/ IOC8T cards for further information on connecting

sensors.

5.3.2DC outputs

Eight DC outputs (DCOUT1 to DCOUT8) are available on the IOC8T card. These can

output fully-processed values from single channels or multi-channels.

By default, the IOC8T card’s DC outputs are configured to provide current-based signals with

a DC output signal range of 4to25mA. Outputs are configured using the VM600 MPSx

software. For example, a 4to20mA output corresponding to a 25to100°C (77to212°F)

input signal (processed value).

The actual value of a DC output can go outside the specified output signal range, depending

on the configured input signal and the load on the output.

For example, if a 25to100°C (77to212°F) signal actually goes from 25to105°C

(77to221°F), the output signal should remain linear outside of the specified DC output signal

range (up to the circuitry limits of approximately 4to25mA for a load ≤440Ω)