Page 10 ams Datasheet
Document Feedback [v1-00] 2015-Mar-30
HLS-442 − Electrical I nterface
Status
The figure below defines the status encoding of b1 and b2:
Figure 10:
The Status Encoding of b1 and b2
Part Number
The part number defines the release number encoding of
b3-b7.
PWM
This section describes the PWM output that is available on
request for the HLS-442.
Physical Interface
The electrical connector is the same as in the variants with CAN
bus interface (see Electrical Connector). The power can be
applied to any of pin 3–5 (Power UB0–UB2). In the case of PWM
output, it does not matter which of these pins that are used.
The PWM signal is created as a differential CAN signal on pin 1
and 2. A CAN signal is said to be in a dominant state when the
signal lines are separated (a dominant bit is transmitted). When
the signal lines are at the same voltage level, the state is
recessive. Recommended circuitry to convert CAN signals to
TTL is specified in a separate document, available on request.
The PWM signal is only an output signal. No messages can be
sent to the sensor.
The PWM Signal
The PWM signal has a period time of 255 μs. The rather short
period is chosen since modern CAN transceivers do not allow
for a longer dominant state.
The duration of the recessive state can be translated into output
H
2
prediction from the sensor module. The recessive duration
(pulse width) ranges from 20 to 240 μs, which corresponds to 0
to 4.4% hydrogen. An internal error is shown as a 10 μs pulse
width.
The figure below shows the output for 0% hydrogen (pulse
width of 20 μs).
Status Encoding b2:b1 Name Description
0 0:0 No error Sensor fully functional
10:1Minor error
Main function ensured, but possible impairment
of measuring quality.
2 1:0 Minor functional error
Main function ensured, but impaired (the sensor
should be replaced)
3 1:1 Fatal functional error Sensor is not functioning correctly.
