ITH
Well-Known Member
Acquired an analogue VDO log (late 1980s) but no paddle wheel transducer. As an electrical dunce, is there a way I can test the instrument to check if it's working - before I start hunting for a transducer?
Old VDO log
- Thread starter ITH
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johnneale
Well-Known Member
Electronic transducers are of two main types - oldest was a reed relay in the transducter operated when the magnet in the paddlewheel passed it by. You can test this by rapidly shorting out the input and +.
The other type is with the magnet inducing a pulse within a coil imbedded in the transducer - to test this you need to connect some sort of coil (like an old transformer or something) and put it close to a 50Hz mains. DO NOT CONNECT IT TO THE MAINS. - this should give a reading of 6 knots.
I used to make logs like this using Jaguar rev counters taken from car breakers.
If the head is working - you will have to get the right sort of transducer. Use a meter to check. A relay one will be open circuit for most of the time, whilst the inducted one will have a permanent resistance of over 1000 ohms
The other type is with the magnet inducing a pulse within a coil imbedded in the transducer - to test this you need to connect some sort of coil (like an old transformer or something) and put it close to a 50Hz mains. DO NOT CONNECT IT TO THE MAINS. - this should give a reading of 6 knots.
I used to make logs like this using Jaguar rev counters taken from car breakers.
If the head is working - you will have to get the right sort of transducer. Use a meter to check. A relay one will be open circuit for most of the time, whilst the inducted one will have a permanent resistance of over 1000 ohms
ITH
Well-Known Member
John, thanks for the info, and I'll give it a go.