Flintec LAC 74.1 - Manual (Page 4)

Current output: The I
out
range can be set to 0 – 20 mA or 4 – 20 mA.
Voltage output: 0 – 10 V output only if current output 0 – 20 mA is selected.
Low-pass filter:
By combining the four DIP-switches the low-pass filter can be set from 0.33 Hz up to 33 Hz.
Factory default is 33 Hz.
DIP-switch ON none 1 2 3 4
Time constant ms 5 16 50 160 500
Settling time ms 40 130 400 1300 4000
Cut off frequency Hz 33 10 3.3 1 0.33
4. Output current (or voltage) adjustment
Use a digital multimeter with at least a 5 digit display. Connect to current or voltage output as
appropriate.
Remark: The multimeter should have a current resolution of 0.01 mA to get a calibration
accuracy of 0.05%.
5. Setting Zero
With no load on the weighing system, use the Zero DIP-switches to initially set the zero value
coarsely to approximately 4 mA (or whatever value you want at no load). Then use the fine
zero potentiometer to make the final adjustment.
6. Setting the Span (Gain)
If you know that you will need to change the gain substantially, it is best to adjust the span
DIP-switches first and then reset the zero prior to applying any loads. For instance if you are
only using 40% (8 mV) of the load cell range (20 mV) you will need to increase the relative gain
to 4x (DIP switch 5 on). See Gain table overleaf. Apply the calibration load and use the fine
potentiometer to give the required result.
Stages 5 and 6 may have to repeated to achieve the required results.
7. Weighing system ready for use
The weighing system is now calibrated and ready for use.
8. Safety
If a short circuit occurs on the load cell supply wires, output wires or sense wires, the output
from the LAC 74.1 will fall to zero as a fail safe condition. With the 4 – 20 mA range selected, an
open circuit in the 4 – 20 mA loop will also be detected as a fault. Under fault conditions the
4 – 20 mA output will fall to 4 mA. If the input signal from the load cell(s) is greater than 4 mV/V
(in a fault condition) then the output will also fall to zero. The fault condition is also signaled by
the release of the FAULT output (normally closed, open collector) and by the red “ERROR”
status LED.
...the right weigh
FLINTEC
Page 4 Manual LAC 74.1