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Some measurements on coaxial relays
Here are some measurement of opening and closing times on RF coaxial relays under various conditions. These measurements were done mainly to have an idea of the timings needed for a relay sequencer.
The measured relay were:
Unless otherwise noted, for all the measurements a freewheeling diode (a 1N4007) was connected in parallel with the relay coil.
Some measurements were also done using zener diodes as freewheeling diodes to check the effect on the relay opening time.
Amphenol 303-10167-3
This is a nice big microwave relay with N connectors, sometimes found at reasonable prices on eBay or flea markets.
Here are the timings when the relay closes (voltage applied to the coil):
after voltage is applied, the normally closed contact opens cleanly in about 12 ms and the normally open contact starts to close in 15 ms, bounces a few times and finally remains closed after 19 ms.
Timings when the relay opens (voltage removed from coil):
after removing the coil voltage, the closed normally open contact takes about 19 ms to cleanly open and the open normally closed contact starts bouncing at 23 ms and finally remains closed after more than 40 ms.
Note that the voltage across the coil remains slightly negative for more than 50 ms, while the energy stored in the coil is dissipated.
MA 7524-PND
Another big microwave relay with N connectors, from Microwave Associates, also sometimes seen on eBay and at flea markets.
Three different relays were measured, to see if there were significant differences in switching times.
One relay was also measured using zener diodes as flywheel diode to see the difference in the release time.
S/N 5584
Timings when closing (voltage applied to the coil):
the NC contact opens with some bouncing after about 4 ms and the NO contact closes, also with some bouncing, after about 10 ms.
Timings when the relay opens (voltage removed from coil):
after removing the coil voltage, the closed normally open contact takes about 11 ms to open and the open normally closed contact starts bouncing at 20 ms and finally remains closed after about 24 ms.
The voltage across the coil remains slightly negative for about 30 ms.
S/N 5634
Timings when closing (voltage applied to the coil):
the NC contact opens with some bouncing after about 4 ms and the NO contact closes, also with some bouncing, after about 8 ms.
Timings when the relay opens (voltage removed from coil):
after removing the coil voltage, the closed normally open contact takes about 13 ms to open and the open normally closed contact starts bouncing at 16 ms and finally remains closed after about 23 ms.
The voltage across the coil remains slightly negative for about 30 ms
S/N 6407
Timings when closing (voltage applied to the coil):
the NC contact opens with some bouncing after about 3 ms and the NO contact closes, with a lot of bouncing, after about 8 ms.
Timings when the relay opens (voltage removed from coil):
after removing the coil voltage, the closed normally open contact takes about 13 ms to open and the open normally closed contact starts bouncing at 17 ms and finally remains closed after about 24 ms.
The voltage across the coil remains slightly negative for about 30 ms
Relay opening times with zener freewheling diode
To reduce the time needed to release the contacts when the coil voltage is removed, a zener diode can be used as freewheling diode instead of a normal diode. This will allow the coil voltage to go more negative during the release time so that the energy stored in the coil will be dissipated faster on the diode.
Here are the relay release timing when an 8.2 V zener is used as freewheling diode:
after removing the coil voltage, the closed normally open contact takes about 6 ms to open and the open normally closed contact starts bouncing at 10 ms and finally remains closed after about 15 ms.
The voltage across the coil goes negative to about 16.5 V for about 12 ms.
When using two8.2 V zener diodes, to allow the coil voltage to go even more negative during release:
after removing the coil voltage, the closed normally open contact takes less than 5 ms to open and the open normally closed contact starts bouncing at 7 ms and finally remains closed after about 13 ms.
The voltage across the coil goes negative to about 8.2 V for about 8 ms.