[Help Request] Question about instrument response time
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For typical measuring instruments, such as pressure transmitters, the response time is the time it takes for the instrument’s output signal to reach 63.2% of its new steady-state value. However, thermal resistors/thermocouples typically use the time it takes to reach 50% of the new steady-state value as their response time. Does anyone know why? I need help, thank you all!
Time constant and response time are two different concepts. The time constant refers to the time it takes for the response to change to 63.2% when a step stimulus is applied; this value is typically denoted as T ； Response time refers to the time it takes for the response to change to a certain specific value when a step stimulus is applied. For thermal resistors/thermocouples, the response time is usually defined as the time it takes for the response to reach 50% of its final value, denoted as T0.5; it can also be defined as the time it takes for the response to reach 95% of its final value, denoted as T0.95. Broader concept: Since the response process can be a aperiodic process or an oscillatory process that decays, the time it takes for the response to reach its first peak is also considered the response time.
Thank you very much. Could I ask again why 63.2% was chosen for the pressure transmitter and 50% for the thermometer? Is this a standard practice? Is 63.2% also usually chosen for other instruments?