Manual

7 | Bases for measurement PTM-100
18 / 26 B-H86.0.02A.DB214-1.0
7 Bases for measurement
7.1 Sensor/device accuracy
The product can be equipped with different interchangeable sensors. Temperature
sensors are categorise in the following classes.
EN 60751
Class Deviation Range
B +/- 0.3 °C +/- 0.5 % of
measurement
-50 … +500 °C
A +/- 0.15 °C +/- 0.2 % of
measurement
-30 … +300 °C
AA = 1/3 DIN B +/- 0.1 °C +/- 0.17 % of
measurement
0 … +150 °C
NOTE
In order to achieve high exchange accuracy without the necessity of an additional cor-
rection, we recommend using Class A or AA temperature sensors.
7.2 Possible measuring errors
7.2.1 Immersion depth
Liquids
Immerse to a depth of at least 20 mm and then stir. Otherwise, measuring errors can
occur due to the heat transmission of the sensor tube if the immersion depth is too
shallow.
Gases
Immerse as far as possible into the gas to be measured so that the measuring sensor
is subjected to a heavy flow.
7.2.2 Surface effects and poor heat transfer
Surface temperature
Special measuring sensors are required for this purpose. Surface characteristics,
design of the measuring sensor, heat transfer and environmental temperature influ-
ence the measurement result.
NOTE
Thermally conductive paste between the measuring sensor and surface can also in-
crease measurement accuracy in some cases.
7.2.3 Cooling / evaporation
Air temperature
The measuring sensor should be dry; otherwise the temperature measurement is too
low.
7.2.4 Response time
Response time T
90
An adequate wait time must be observed for the measuring process before reading
the measured value. The response time T
90
describes the time in which the displayed
measured value reached 90% of the end value. See Technical data [}p.25].