PUB6438S Honeywell Central control module Brand new

ATTENTION

In redundant PIM modules, after a switchover, if the alarm for the reported channel still

persists on the new primary, this most likely indicates a problem in the field wiring.

6.2 Field device output stage types

The output stage of most field sensors use an open collector bipolar transistor or an open drain

MOSFET to produce a pulse for counting by a metering device. Open collector and open drain

transistors require an externally supplied pull-up resistor and a source of dc power for transistor

action to take place. Other types of sensor outputs may incorporate a push-pull, totem pole (for

example TTL), or differential output stage which delivers fast rise/fall time pulses without the need

of a pull-up resistor. Although not as common, some field sensors contain an open emitter or open

source transistor for the output stage. This type requires an externally supplied pull-down resistor.

PIM has been designed to operate with all of these types. This section provides information on the

specific type and provide guidelines on the connectivity of each.

Figure 6.2 Field device output stage types

ATTENTION

Millivolt signals are not counted by the PIM unless a suitable preamplifier is used to boost

the signal to a level that can be detected by the PIM circuitry.

6.3 PIM resistor bias terminal blocks

The PIM IOTA provides eight terminal blocks (one for each channel) that enable the user to install

the appropriate bias resistor for proper operation with the field device.

l Pull-up (open collector or open drain output stage)

l Pull-down (open emitter or open source output stage)

l No bias (Active drive - differential, Transistor-Transistor Logic (TTL), and so on)

The following figure displays the channel 1 RES BIAS terminal block.