Beckhoff EPP3504-0023 Short Manual page 29

The numerical values used in the following three examples are for illustration purposes. The specification
values given in the technical data remain authoritative.
Example 1:
Basic accuracy of an ELM3504 at 35 °C ambient temperature, measurement of -100 °C in the PT1000
interface (4-wire), without the influence of noise and aging:
T = -100 °C
Measuring point
MW = R = 602.56 Ω
PT1000, -100 °C
= 86.238 ppm
FSV
E (R ) = 86.238 ppm
Resistance Measuring point
ΔR (T ) = (R(-99 °C) – R(-100 °C)) / (1 °C) = 4.05 Ω/°C
proK Measuring point
E = (0.1725 Ω)/(4.05 Ω/°C) ≈ 0.043 °C (means ±0.043 °C)
ELM3504@35°C, PT1000, -100 °C
Example 2:
Consideration of the repeatability alone under the above conditions:
T = -100 °C
Measuring point
MW = R (-100 °C) = 602.56 Ω
Measuring point
E = 10 ppm
Single FSV
E = 10 ppm ⋅ 2000 Ω = 0.02 Ω
Resistance FSV
ΔR (T ) = (R
proK Measuring point -99 °C
E (R ) = 0.02 Ω / 4.05 Ω/°C ≈ 0.005 °C (means ±0.005 °C)
Temp Measuring point
Example 3:
Consideration of the RMS noise alone without filter under the above conditions:
T = -100 °C
Measuring point
MW = R (-100 °C) = 602.56 Ω
Measuring point
E = 37 ppm
Single FSV
E = 37 ppm ⋅ 2000 Ω = 0.074 Ω
Resistance FSV
ΔR (T ) = (R
proK Measuring point -99 °C
E (R ) = 0.074 Ω / 4.05 Ω/°C ≈ 0.018 °C (means ± 0.018 °C)
Temp Measuring point
Example 4:
If the noise E of the above example terminal is considered not for one sensor point -100 °C but in
Noise, PtP
general, the following plot results:
EPP3504-0023
⋅ 2000 Ω = 0.1725 Ω
FSV
– R ) / 1 °C = 4.05 Ω/°C
-100 °C
– R ) / 1 °C = 4.05 Ω/°C
-100 °C
Version: 1.2
Product overview
29