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Measurement principle of FSM3 Series
The FSM3 Series incorporates a platinum sensor chip machined with silicon micro-machining. The sensor is thermally
insulated from the silicon substrate. The heating capacity is extremely low, enabling high sensitivity with a high-speed
response.
At the sensor, two temperature sensors are arranged with a heater in between. Platinum, which has a resistance
that changes based on temperature, is used for the temperature sensor. When the heater is turned ON and heating
occurs, the temperature distribution is symmetrical to the center of the heater if there is no flow. When flow is received,
the symmetrical property of the temperature distribution is lost, temperature upstream from the heater drops, and
temperature downstream rises. This temperature difference appears as the difference in temperature sensor resistance,
and varies with the flow rate. When the flow is reversed, the temperature difference (difference in resistance) will be
inverted. By using this method, the bi-directional flow rate can be detected. This method is suitable for detecting a
relatively small flow rate.
Measurement principle of FSM3 Series
FSM3
Series
[Without ow]
Symmetric temperature distribution
Symmetry of temperature distribution is lost
Temperature sensor (1)
Temperature
Resistance value
Temperature
Resistance value
Temperature sensor (2)
Heater
R1
R1
R1
R1
R1
R1
3.3 V
3.3 V
Voltage
Voltage
V out
V out
V out
V out
1.65 V
1.65 V
Rh
Rh
R2
R2
R2
R2
R2
R2
[With ow]
FLOW
LCD display Bar display
IO
-
Link
Internal
structure
Separate
display
Technical
data
Operating
method
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products
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precautions
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