Temperature sensor

In Circulo a specific temperature sensor port with selectable integrated pull-up resistors is available. This input port is suitable for RTD sensors because of its high input resistance (1 MΩ). Alternatively, the single-ended 5 V Analog input with an external pull-up resistor can be used as an RTD sensor input as well.

For details about using temperature sensors, please refer to our system integration guide

A reference voltage of 5 V is supplied. The sensor’s recommended current is typically about 1 mA (please refer to the manufacturer data sheet). The pull-up resistor has to be selected according to the RTDs data sheet to ensure that the current is not higher or lower than required.


Please ensure that the voltage attached to the temperature sensor input is between 0 V and 5 V.


Synapticon has successfully tested PT1000 and KTY84-130. PT100 will also work but be aware that its low resistance will result in a low accuracy so this type can’t be recommended.

In case you want to use other sensors, such as NTC, please contact support@synapticon.com.

Circulo 7Circulo 9Circulo 7
Circulo 9

Circulo offers three different configurable integrated pull-up resistors: 4.7 kΩ, 10 kΩ and 22 kΩ.

Depending on the type of temperature sensor, different resistors in the servo drive need to be activated. This is done internally with a multiplexer. The desired value can be selected via software through object 0x2038 subindex 3.


The ADC value is scaled to 16 bit since firmware v5.0.

Firmware v4.xFirmware v5.xFirmware v4.x
Firmware v5.x


If you define the different resistor value for the internal ADC input, the firmware will choose the closest resistor to the specified value

The measured analog value can be calculated into a corresponding temperature by the drive itself. Details are described in Analog Input Scaling.

For details about using temperature sensors please check our System integration guide.

Specification for the single-ended temperature sensor input








V in



The input voltage between the input and GND.

Any voltage out of this range causes saturation to the min/max ADC value.

V in,lim



The tolerable input voltage between the input and GND.

Any voltage out of this range damages the analog input’s circuitry.

R i


Internal input resistance




Error in ticks


The temperature sensor input should only be used for measuring temperatures with RTD.