ABUS Technologies Field Logger Data Acquisition/Recorder - Manual (Page 10)

ABUS TECHNOLOGIES INC.
10
Field
Logger
two alarms associated to it. Set-point values and alarm functions (HI or LO) are set in the Alarm 1 and
Alarm 2 boxes, as well as the selection of the output relay for each alarm. If no relay is associated to an
alarm, even so the alarm will be processed and informed to the supervisory software (refer to section –
Serial Communication).
The 2 relays may be configured as alarms, as mentioned previously, or as digital outputs,
controlled by the MODBUS Preset Single Coil command, described in section- Serial Communication.
When configured as digital output (see boxes “Relay 1 function” and “Relay 2 function”), the relay
becomes unavailable to the alarms, even if an alarm was configured to use the relay. Returning the
relay to the Alarm function, all previous alarm configurations will work again.
The odd channels (1, 3, 5, and 7) can be configured as differential, as mentioned in section-
Analogue Inputs. When a channel is configured as differential, the adjacent channel is also used;
therefore, the respective even channel (2, 4, 6 or 8) is disabled in the configuration screen.
7.3 Acquisitions Page
This page contains the parameters needed for recording data in the Field Logger internal
memory. These parameters are:
- Start Logging time
- Stop Logging time.
- Base Interval Between Loggings
- Interval Multipliers for the channels (set individually for each channel).
When a new logging configuration is transmitted, the current PC time and date is updated in the
Field Logger.
Note: Make sure the date and time in the PC is correct before sending a new configuration.
The Field Logger is meant for measuring process variables, prioritizing accuracy and resolution
over speed. The update rate for the input channels depends on the number of active channels and on
the sensor type configured in each channel. It takes 50ms for an input to be converted (measured).
Other internal measurements are needed for improving accuracy (offset suppression and gain
calibration). Besides, cold junction compensation for thermocouples and cable length compensation for
Pt100 measurements are also accomplished, depending on input channel configuration. An estimate
update time for a single channel measurement is 0.2s. For 8 channels with thermocouple inputs, this
time is 0.55s, whereas 8 Pt100 channels require 0.95s for the update.
So, the time interval between loggings should not be set shorter than the total time required for
reading the inputs. This time interval is defined by the Base Interval Between Loggings and the Interval
Multipliers.
The base interval can be specified from 0.2s to many hours and is common to all channels. The
interval multiplier, however, can be configured individually for each channel, allowing distinct logging
rates among channels. For example, for a base interval of 10s, a multiplier 1 will cause a new sample to
be recorded every 10s; for a multiplier equal to 6, the channel will be recorded once every minute. Using