30-07-2015, 08:17 AM
Not really. Hasn't got the power handling capability so it would need to be used with a power device to the actual crowbar.
It's often very easy to devise a complicated system. Cutting through all this to arrive at a simple solution may not always be obvious. There is also Murphy's Law, which tends to be more active in complex designs simply because there is more to go wrong. That's why there's a lot to be said for simple methods. They may not give the very best performance but if they're good enough then that's fine.
Let's contrast this: http://www.dos4ever.com/uTracer3/uTracer3.html and the simple approach that the OP wants to use.
The uTracer is a lovely bit of design, capable of measuring the pants off just about any valve. Done by a skilled design professional who has carefully worked out the tolerances and pitfalls. It's also quite complex, though no more so than it needs to be to do the job. At the other extreme is a lashup of power supplies, meters and clip leads. This is simple, if rather untidy and will also do what's intended. In between you can make up some jigs to avoid the worst of the lashup and make it less prone to silly mistakes. This is roughly what the OP wants to do. I'd just use a bench power supply to run the heater of the valve under test. But then I've got bench PSUs around anyway. If the OP doesn't have one to hand then the variac and transformer arrangment is one of the simplest and most foolproof way of doing it.
It's often very easy to devise a complicated system. Cutting through all this to arrive at a simple solution may not always be obvious. There is also Murphy's Law, which tends to be more active in complex designs simply because there is more to go wrong. That's why there's a lot to be said for simple methods. They may not give the very best performance but if they're good enough then that's fine.
Let's contrast this: http://www.dos4ever.com/uTracer3/uTracer3.html and the simple approach that the OP wants to use.
The uTracer is a lovely bit of design, capable of measuring the pants off just about any valve. Done by a skilled design professional who has carefully worked out the tolerances and pitfalls. It's also quite complex, though no more so than it needs to be to do the job. At the other extreme is a lashup of power supplies, meters and clip leads. This is simple, if rather untidy and will also do what's intended. In between you can make up some jigs to avoid the worst of the lashup and make it less prone to silly mistakes. This is roughly what the OP wants to do. I'd just use a bench power supply to run the heater of the valve under test. But then I've got bench PSUs around anyway. If the OP doesn't have one to hand then the variac and transformer arrangment is one of the simplest and most foolproof way of doing it.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
