The response time indicates how fast a sensor reacts to temperature changes. The test procedure is based on the specifications of DIN EN 60751. However, the specifications of the norm are very general and thus the data are not comparable with the data of other sensor manufacturers. Nevertheless, the data can be used to compare sensors within the Heraeus Nexensos portfolio. Values for response times in water and air are stated in the tables on each product data sheet. Thin Film Platinum (Pt) Resistance Elements have exceptionally short response times. The housing and the potting of the sensor element have the biggest influence on the response time of a sensor probe.
Heraeus Nexensos Platinum RTD Data Sheets State Response Time Data for Each Part. A Response Time Is Stated for “t0.5” and “t0.9”. What Does This Mean?
“t0.5” means the time elapsed to respond to 50 % of a step change in temperature.
Similarly, “t0.9” means the time elapsed to respond to 90 % of a step change in temperature. Let’s use actual response time data from the M222 thin film data sheet (below) as an example:
|water current (v = 0.4 m/s):||t0.5 = 0.05 s|
|t0.9 = 0.15 s|
|air stream (v = 2 m/s):||t0.5 = 3.0 s|
|t0.9 = 10.0 s|
The data sheet states a t0.5 response time of 0.05 seconds in water. This means if an element is exposed to a step change in temperature from 50 to 100 °C, after 0.05 seconds, the element body temperature will be 75 °C (50 % of step change between 50 & 100 °C), and after a total of 0.1 seconds, the element body temperature will be 87.5 °C (50 % of the step change from 75 to 100 °C).
Measuring Current & Self Heating
Measuring Current and Self Heating
Like all resistive elements through which a current flows, Platinum (Pt) Resistance Elements are slightly heated by the current. The magnitude of this "self-heating error" is dependent upon on the electrical energy input (N = I2 x R), the quantity of heat being dissipated, and a component constant. The self-heating constant for each resistance element when used in water or air is shown in the tables on each product page.
How Does the Needed Measuring Current Influence the Self-Heating of the Sensor?
On Our Data Sheets We Talk about Long-Term Stability. What Is This?
On Our Data Sheets We Talk about Insulation Resistance. What Is That?
Shock & Vibration Resistance
Shock and Vibration Resistance
Sensors are subjected to a wide variety of vibration and shock conditions during installation. Vibrations are simulated via oscillations and shock via extreme negative and positive accelerations.
Mounting and connection play a major role and should be considered.To test this requirement, the sensors are mounted on a test table and subsequently subjected to oscillations and vibrations in different directions. According to DIN EN 60751, the test setup passes through different frequency bands over defined times. Subsequently, the components are checked for mechanical damage.
The pull test checks the mechanical connection between the sensor wire/cable and the sensor body. A force is applied to the wire/cable under test until the connection point or the wire/cable fails. The force applied at the time of failure is measured.
The dielectric strength of a sensor is the maximum voltage potential without insulation failure. To test the dielectric strength of a sensor, a test voltage is applied as specified for a customer-specific time between a measuring circuit and the sensor. To confirm the dielectric strength of the sensor, no short circuit may occur during this period.
Temperature & Humidity Test