X-D2A Datasheet, PDF (6/16 Pages) List of Unclassifed Manufacturers – RELAY - NONLATCH 2 PDT, LOW LEVEL TO 5 AMP

Application notes
N°102
RELAYS AND TEMPERATURE VARIATIONS
Most relay parameters are specified as maximum values over the rated temperature range of the specific relay. Users often
find that key parameters differ significantly at ambient temperature (20-25°C) and sometimes fall into the trap of specifying
their system around these ambient parameters. Additionally the actual temperature experienced by the relay can be far in
excess of existing ambient temperatures due to the heat generated by the coil current and the contact load. Figure 1 is the
summary of temperature effects on relay electrical characteristics.
Temperature
Increase
Decrease
Resistance
UP
DOWN
Current
DOWN
UP
Operating
Voltage
UP
DOWN
Release
Voltage
UP
DOWN
Operate Time Release Time
UP
DOWN
UP
DOWN
Fig. 1
The following formulas are sometimes useful in calculating the effects shown above.
1. Change in coil resistance due to change of ambient temperature can be calculated by the following formula.
R = R₂₀ [1 + .0039 (T-20)]
Where: R = Coil resistance at given temperature
R₂₀ = Coil resistance at 20°C
T = °C Ambient temperature
"Rule of Thumb" : For each 10°C change of temperature, coil resistance will change approximately 4%.
2. High and low temperature pick up voltage:
E₂ = E₁K_2,
Where: E₂ = Pick Up Voltage at T₂ temperature
E₁ = Pick Up Voltage at 20°C
K₂ = Coefficient of correction found on the graph in Fig. 2 at T₂
Date of issue: 6/00
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