ambient temperature sensor resistance

With a simple single-ended voltage divider, a 10-bit ADC at 0–5 V gives about 4.9 mV per count. For a 10 kΩ NTC with B=3435, the voltage change around 60°C becomes very small—just a few ADC counts—so accuracy suffers. Consider adding an external op-amp for gain or switching to a Pt1000 with a constant current source; its more linear resistance at higher temperatures makes signal amplification easier.

Platinum RTDs generally show better long-term stability than NTC thermistors. NTC materials can drift slightly under humidity or thermal cycling, but well-sealed, glass-encapsulated NTCs still achieve low annual drift. The trade-off often comes down to budget and how often you can recalibrate. In many geotechnical projects we work on, Pt1000 is preferred because the logger’s current-source design is simpler and multi-channel consistency is better.

If you transmit resistance directly, the copper wire’s own resistance (maybe several ohms to tens of ohms over 200 m) adds to the sensor’s resistance and creates error. For sensors in the kilo-ohm range this may be tolerable, but for a low-resistance Pt100 it can dominate. A 4–20 mA current loop is a common solution, or you can integrate a transmitter to convert resistance to current or voltage at the sensor head. Kingmach supplies temperature probes with built-in 4–20 mA output that suit most industrial input cards.

First, see what the module accepts: 0–10 V, 4–20 mA, or direct RTD/thermistor inputs. Many PLC modules with RTD channels support Pt100/Pt1000 and perform internal linearization. If you only have voltage inputs, a voltage divider can convert the thermistor’s resistance to voltage, but you need to account for the divider resistor’s temperature coefficient and the ADC input impedance. Compare the sensor’s output range—resistance or voltage—against the module’s range. We can provide wiring diagrams and reference circuits for common setups.

Standard values like 10 kΩ or 100 kΩ at 25°C are readily available, but if you need a specific B-constant or tighter tolerance, we work with thermistor manufacturers who can handle custom resistance, B-value, and accuracy—though minimum order quantities may apply. As an alternative, we often recommend integrating a microcontroller at the sensor for local linearization and digital output (Modbus RTU, for example). That simplifies compatibility on the data-collection side.