51303991-100 Honeywell Programmable controller Brand new

Low Latency Mode

When the DIMODE parameter in DI24V and DI-SOE IOM FB is set to LowLatency, the channel's

inputs are sampled and processed every 5 msec for better response times when using Discrete

Loops that require low latency responses. In the case of DI-SOE, SOE event generation is not

supported when DIMODE is LowLatency. This mode will also not support Open Wire Detection.

12.12.2 OWDENBL changes in Project View

The following Open Wire Detection changes occur when the initial value of DIMODE = LowLatency

DIMODE and is modified:

l Changing the OWDENBL parameter value to TRUE is not allowed in LowLatency and SOE

modes.

l If this is done, the following error is displayed: 'Open Wire Detection cannot be enabled if

DIMODE of IO Module is configured as LowLatency or SOE.'

12.13 Enabling pulse proving in Pulse Input Module

To improve metering accuracy, turbine meters used for custody transfer purposes are often

“proved” in situ using the real process fluid at the correct flow rate. When a meter is being proved,

its flow is diverted such that the prover is downstream and in series with the meter. Thus the same

flow passes through the meter and the prover in series.

The prover is basically a length of pipe. Inside the pipe is a sphere which is driven around the pipe

by the pressure of the flow. In a bi-directional prover, the sphere can move in the forward or

reverse direction as determined by the position of the 4-way valve. As the sphere moves around

the pipe, it passes sphere detection switches. The swept volumes between all sphere switch

combinations (that is 1 and 3, 1 and 4, 2 and 3 and 2 and 4) are determined offline and are known

extremely accurately. The sphere switches are used to turn on and off a copy of the good pulses

from the meter being proved. Thus a total number of pulses can be obtained versus a known swept

volume and so the actual K factor of the meter being proved can be determined.