13
Warning
Yellow
LED
Green
LED
Red
LED
Error output
Offset adjustment
necessary
1
Flashes
on
off
off
Alarm
Yellow
LED
Green
LED
Red
LED
Error output
Interpolator electronics
errors
2
Flashes
off
Flashes
Pulse
Error at pick-up
3
off
on / off
on
on
Flow overload
on
off
on
on
max. frequency range
exceeded
(>100 kHz)
4
on
on
Flashes
Pulse
Fluid temperature
> 120°C
5
Flashes
on
Flashes
Pulse
Table 6: Alarm and warning messages
17. Alarm and Warning Messages
The electronics of the FHG flow meters can detect five events that could
lead to measurement errors. In case of serious errors, the third output has
a ”high“ signal or a ”pulse“ signal if activated with the bridge B1. The
different error causes can be determined with the states of the three LEDs.
The red LED is linked with the error output. Each active state of this LED or
the error output signals an event that has negative effects on the measure-
ments.
Description of the Error Messages
1. Offset adjustment necessary: The sensor and/or the preamplifier elec-
tronics were replaced. A different size was set.
2. Electronics errors: Defective component in interpolator circuit, unable to
determine internal configuration values
3. Pick-up errors: The sensor is defective or quit working. The distance bet-
ween the sensor and the magnet wheel has changed = mechanical
damage
4. Overload: The maximum permissible flow range was exceeded
5. Frequency errors: The max. output frequency of 100,000 Hz was excee-
ded. The IPF is dimensioned too high for the respective flow
6. Temperature errors: The temperature of the fluid is too high (> 120°C)
and may result in flawed or incorrect measurements
18. Preamplifier Technical Data
Scanning sensor
2 x GMR sensors in a bridge circuit (sin/cos)
Adjustment
automatic offset adjustment
Resolution
programmable 1, 2, 5, 10, 25, 32, 50, 64, 100, 128
Adjustable pulse filtering
0Z, 0.25Z, 0.5Z, 0.75Z, 1.0Z, 1.25Z, 1.5Z, 1.75Z, 2.0Z, 2.25Z, 2.5Z, 2.75, 3.0Z, 3.25Z, 3.5Z, 3.75Z (Z: gear unit)
Frequency
up to 100 kHz
Output signals
Channel A, channel B, directional signal DIREC (high: positive, low: negative) or error signal ERROR
(high or pulse: error)
Channel A and B
two signal outputs for outputting the digital flow sensor signals, a channel offset of 90° between channel A and
channel B;
Flow direction
Detection of flow direction from the channel offset of the signals from channel A to channel B or via the separate direc-
tional signal.
Outputs
Three current-limited and short-circuit-proof power amplifiers (channel A, channel B, DIREC / ERROR); integrated
adjustment to a characteristic impedance of 75 Ω; driver current approx. 300 mA at supply of 24 V; small saturation
voltage of up to 30 mA load current, short switching times, integrated freewheeling diodes against V
b
and GND, ther-
mal shutdown with hysteresis; in case of error, the outputs are high impedance;
The 24 V line drivers are designed for control applications with cable adjustment
Error messages
Electronics fault (e.g. faulty interpolator), sensor errors (e.g. sensor failure), offset adjustment necessary, overload (flow
peaks), frequency error (> 100 kHz), temperature error (> 120°C)
Operating voltage
V
b
= 10 … 28 VDC
Current consumption
l
noload
= approx. 40 mA, total current consumption depends on output load
