Let's see if I have the sequence correct, on the 27th, the resistor had been 'cooked' over night so any humidity inside was minimal for the first test. Rate of temperature change 0.12°C/minute.
On the 29th, resistor had been sitting at room temperature for two days in moderate humidity before testing, resistor showed odd reading. Rate of temperature change 0.3°C/minute.
On the 1st, the same resistor had been sitting at room temperature and similar humidity, the only 'difference' was the rate of temperature change, 0.12°C/minute. Readings appeared about normal.
I have a question or two for you. How many cycles of cold and hot do you do before the resistor rests? Any particular reason why you chose a different rate of temperature change for the second test?
Hello Edwin,
the number of cold and hot cycles depends a bit on how much time I have on the day when I am soldering.
I try to do a (fast) cold and warm cycle after soldering. But this does not happen always.
For Z201#2 the history is as follows: (It was a saturday so I had some time).
Soldering on 26th after this a fast heating to 45 deg C
Fast cool down to 25 deg.
Fast cold cycle to 10 deg C.
Fast heat up to 25 deg
Fast heat up to 45 deg (over night)
Where fast means in this case: as fast as my equipment can.
(picture attached)
On 27th in the morning a fast cool down to 25 deg C
from this the measurement beginning with a cold cycle 0.12 deg/minute.
on 28th no measurement just room temperature.
On 29th the measurement (3 cycles) with 0.3 deg / minute.
On 30th+31th no measurement just room temperature.
On 1st the measurement 1 cycle with 0.12 deg/minute.
(pictures already shown in previous posts)
The different rates have several reasons.
with several cycles within one measurement I want to see wether there are some ageing
or hysteresis effects which change over time.
(0.3 deg/K gives up to 3 cycles per day).
With the slow ramp I wanted to see if the hysteresis has something to do with thermal delay.
So if the ramp speed is factor 2.5 slower then a "hysteresis" due to thermal delay (between resistor
and themperature sensor) should also change by factor 2.5.
But since the factor observed does by far change not that much the root cause of the hysteresis
is not (primary) a temperature sensing problem.
I also had different effects on hysteresis with different ramp speeds of (different types of) voltage references,
so I wanted to see if it has also a influence on resistors.
So Z201#2 is the first candidate where I see something unusual.
With best regards
Andreas