Diode bridge for ammeter?

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elephant
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Diode bridge for ammeter?




by elephant » 12/09/13, 11:26

Is there a diode bridge to place an ammeter?

The problem is to measure the charging current ou discharge between a battery and its charger with an ordinary DC ammeter (so not a central zero ammeter: I made the sales :D ) without switching (not manageable because the charger regularly interrupts the charge itself to test the battery.

The ammeter is therefore inserted between the + of the charger and the + of the battery, but the current changes direction.

No need to tell me Graetz Bridge, this is to measure tensions.
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by I Citro » 12/09/13, 13:56

: Arrowu: I don't really understand. :?
The battery sends current to the charger. :?:

I imagine you want to measure the current produced by the charger, so by inserting the ammeter between the charger and the battery.

If you want to measure the current consumed by the equipment powered by the battery, you just need to insert another ammeter between the battery and the consumer.

You have to tell us a little more ... :?
It is a loader / unloader. :?:
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by elephant » 12/09/13, 14:36

This involves continuously measuring the charge quality et the consumption of alarm control panel batteries.

what interests me is to measure the discharge (to predict the autonomy), but usually the battery (lead) is in a state of charge. (buffer use)
There is no question of disconnecting, otherwise, the control unit will reset to zero when the current returns after the discharge test
But I only have a 0-5A needle ammeter, not a central zero device; It would therefore be necessary to mount diodes so that the current always flows in the right direction in the ammeter [/ b]
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by chatelot16 » 12/09/13, 14:51

you can put a diode bridge, but the diode voltage drop will disturb the charger: an ordinary silicon diode loses 0,7V so a bridge loses 1,4V since there are 2 in series

one solution is to put a rotary inverter with full short circuit during the reversal

there existed in old equipment this kind of inverter ... at a time when we built the special devices we needed

with this assembly, when you put the control button in position 0 you can disconnect the ammeter without cutting the power to use it for something else
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by elephant » 12/09/13, 15:12

Chatelot, the question is: which diode bridge?
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Re: Diode bridge for ammeter?




by Alain G » 12/09/13, 15:34

elephant wrote:Is there a diode bridge to place an ammeter?

The problem is to measure the charging current ou discharge between a battery and its charger with an ordinary DC ammeter (so not a central zero ammeter: I made the sales :D ) without switching (not manageable because the charger regularly interrupts the charge itself to test the battery.

The ammeter is therefore inserted between the + of the charger and the + of the battery, but the current changes direction.

No need to tell me Graetz Bridge, this is to measure tensions.


Hello Elephant!

This is useless because the charger only checks the battery voltage and your ammeter will not feel it having a current reversal but if you really want a simple low resistance diode will do the job unless that you really care to know the amperage of battery check by your charger.

Note that a diode will distort the reading of your ammeter by its internal resistance and at the same time the reading of your battery by your charger, therefore not recommended.
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by elephant » 12/09/13, 15:54

AlainG said:

your ammeter will not feel it to have a current reversal


???? aren't you going to tell me that my ammeter won't suffer from being plugged in the wrong way?
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by chatelot16 » 12/09/13, 15:56

which diode bridge? my answer is that a diode bridge is not suitable between a charger and a battery!

the simplest is to put an ammeter that works in both directions like the digital multimeter

with a needle ammeter there is a way to do it: shift the zero: the precise ammeter we always have this kind of adjustment of the fixed point of a spiral spring

in general we cannot put the point of rest in the middle, but at 1/4 or 1/3 of the race: that is enough to be usable
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by chatelot16 » 12/09/13, 16:06

the heating of the ammeter is the same at the place or upside down

that the needle takes a normal position, or is in abutment against zero does not tire it more

so there is no danger in leaving an ammeter plugged in backwards

you ask for a solution without switching: but it is possible to switch cleanly: mount a switch which passes the current in place of the ammeter! when the switch closes the circuit you can disconnect the ammeter to change its direction, then open the switch to measure
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by elephant » 12/09/13, 16:31

In fact I had a back-up solution: 1 NF pusher in // with the galvanometer, but I was looking for a more elegant solution.

Thank you to all :D
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