BECKHOFF KL3681 - Manual (Page 9)

Product overview
• AC/DC voltage measurement, automatic range selection: “Autorange” or specified via the controller
Measurement ranges: 300 mV, 3 V, 30 V, 300 V
• AC/DC current measurement in the 1 A path (internal fuse: 1.25 A) or 10 A path (no internal fuse)
Measurement ranges: 100 mA, 1 A, 10 A
• Formation of measured values:
Alternating current and alternating voltage are calculated as true RMS values, no DC component
Direct current and direct voltage are calculated as arithmetic average value
• Electrical isolation from the fieldbus
• Very good interference immunity through dual­slope conversion technique
• Display of measurement type (current/voltage) and overload through LED
• Typical update rate approx. two seconds, after measuring range change approx. one second
Quick start
The factory setting for the multimeter terminal enables voltages up to 300 V
DC
to be measured directly
without additional settings. The Autorange function is active and selects the measuring range automatically.
The measured value is displayed with 1 bit per microvolt, i.e. no adjustment is required.
Functional description
Measuring ranges and output
The terminal starts measuring automatically. New measurement readings will be put out as soon as the
calculation is complete. If the last used and the requested measuring range do not match, the bit “Data
invalid” is set. In the event of an error (generally measuring range exceeded) the respective error bits are
set. New measurement values are provided approx. every 0.5 seconds. The filter time is reset if the
measuring range is changed via Autorange or by the user during the filter period. If the value fluctuates too
much in Autorange mode, it may not be possible to determine a new measured value. As a remedy the filter
can be deactivated.
The terminal has an extended measuring range, if a larger measuring range is available (Example: 30 V
range, extended measuring range is 300 V). In Autorange mode the extended measuring range is used as a
hysteresis range. In the extended measuring range overflow and underflow bits and the error bit are set at
115 % of the normal measuring range.
Note
Please note
• In AC mode only the RMS value of AC voltage is shown (no DC component).
• Error bits are under­range, over­range and data invalid. The error bit is set together with
these bits. In some cases several bits may be set simultaneously in the event of an er­
ror (e.g.: Overrange and Data invalid).
• Since the terminal integrates the input value over an interval of 20 ms (16.66 ms in
60 Hz mode), superimposed interferences of the input values from the supply network
can largely be compensated.
Measuring range selection
The measuring range is selected in process data mode via the control byte [ } 28].
The Autorange function selects the best measuring range for the selected measurement type. In Autorange
mode the 10 A measuring ranges are distinct types of measurement, i.e. it is not possible to switch from 1 A
and 10 A or back (Causes: different input contacts as like fuse protection of the1 A range with 1.25 A).
The limits for changing the measuring ranges range are 10 % above the full scale value (extended
measuring range, larger range) and 10 % of the full scale value (smaller range). If "Left aligned" view is
selected, the limits are 100 % and 5 % of the full scale value.
KL3681, KS3681 9 Version 2.0.0