5.3 Description of Function Codes 5.3.5 H codes (High performance functions)
Thermistor (for motor) (level) (H27)
H27 specifies the detection level (expressed in voltage) for the temperature sensed by the PTC thermistor.
• Data setting range: 0.00 to 5.00 (V)
The alarm temperature at which the overheat protection becomes activated depends on the characteristics of the
PTC thermistor. The internal resistance of the thermistor will significantly change at the alarm temperature. The
detection level (voltage) is specified based on the change of the internal resistance.
Suppose that the internal resistance of the PTC thermistor at the alarm temperature is Rp, the detection level
(voltage) Vv2 is calculated by the expression below. Set the value of Vv2 to function code H27.
Connect the PTC/NTC thermistor as shown below. The voltage obtained by dividing the input voltage on terminal
[V2] with a set of internal resistors is compared with the detection level voltage specified by H27.
When using the terminal [V2] for PTC/NTC thermistor input, it is necessary to change wth switch (SW5)
on the control PCB. Refer to Chapter 2 “2.2.7 Operating slide switches”. for details.
PTC thermistor
internal resistance
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