I've joined this newsgroup to try to get some help on a particular
problem. I decided as a winter project on the boat to replace analogue
voltmeter and ammeter with digital ones from Lascar. I was recommended
these as being suitable and ordered them from the website:

http//:www.lascarelectronics.com

They have now arrived. No problem with wiring in the voltmeter but I am
stuck over how to wire in the milli-volt meter in a way that it can be
used to measure amps in my 12 volt circuit. I understood it could be
used to measure voltage difference on either side of a 0.1 ohm shunt to
give a value in amps. This may well be the case but the fact it comes
with ten wires, a small circuit board and four extra resistors was a bit
of a shocker to someone like me who just about knows the difference
between amps, volts and watts.

I realise this is a big ask but if anyone has the time and knowledge I
would be very interested to hear from them. It is the EMV 1125 meter and
there is a two page data sheet available from this page.

http://www.lascarelectronics.com/pro...01125&CFID=337
6245&CFTOKEN=35600876

David

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Hello David,

Based on the data sheet, the EMV 1125 is a general purpose panel meter
that the user configures for specialized applications.

It can be used to measure voltage (see the illustration at the bottom
left of the second page) but it is not really what you want. These GP
digital panel meters come in two flavors: those that will work from the
same power source they are measuring, and those that require a power
source independent of that being measured. The EMV 1125 is the latter
type, unfortunately.

To make this work, the simplest solution would be for you to connect a 9
volt battery (preferrably alkaline) to the two terminals marked Supply
Voltage, observing plus and minus polarity. (The garden variety digital
voltmeter actually works this way).

Next, connect the two terminals on the right-hand side of the board
across the shunt. One wire to each side of the shunt. The minus terminal
on the board should go to one side of the shunt and the plus to the
other side. If you mix them up, the meter will simply display a minus
sign in front of the reading. If that happens, just switch the wires.
Depending on where the shunt is located in your boat's wiring, you might
actually want both positive and negative readings, depending on which
way the current is flowing through the shunt.

It appears that the ten wires on the board relate to the ten
corresponding terminals on the meter itself. They appear to be
color-coded. 0,1,and 2 should be connected from the board to the meter.
3,4, and 5 seem not to be required. Choose which of the decimal point
positions best suits your shunt. You want to be able to display full
shunt voltage (maximum current) on the meter. Suppose you need to be
able to measure up to 199.9 millivolts. Then you would connect the
violet wire from the meter to pin six on the board (DPCOM). Tape the
ends of the unused wires.

If you'd like to verify this with Lascar, I noticed a Technical Support
page where you can just cut and paste this.

The obvious downside to this solution is that you need to use a 9-volt
battery. You could put a push-button switch in series with the positive
lead to the 9-volt battery and thus read current only when the button
was pushed. The 9-volt battery would last for years with that kind of
usage.

The next simplest approach is to return the device and choose one that
does not require an independent power source.

The last, and potentially most difficult, solution is to locate a dc-dc
converter that will provide 12 vdc to power the meter that is isolated
from the 12 vdc of your boat battery. Probably not worth the bother.

The 9-volt battery solution is really quite straightforward and you
should experience no difficulties. Let me know if you have any further
questions.


Chuck







David Pocock wrote:
I've joined this newsgroup to try to get some help on a particular
problem. I decided as a winter project on the boat to replace analogue
voltmeter and ammeter with digital ones from Lascar. I was recommended
these as being suitable and ordered them from the website:

http//:www.lascarelectronics.com

They have now arrived. No problem with wiring in the voltmeter but I am
stuck over how to wire in the milli-volt meter in a way that it can be
used to measure amps in my 12 volt circuit. I understood it could be
used to measure voltage difference on either side of a 0.1 ohm shunt to
give a value in amps. This may well be the case but the fact it comes
with ten wires, a small circuit board and four extra resistors was a bit
of a shocker to someone like me who just about knows the difference
between amps, volts and watts.

I realise this is a big ask but if anyone has the time and knowledge I
would be very interested to hear from them. It is the EMV 1125 meter and
there is a two page data sheet available from this page.

http://www.lascarelectronics.com/pro...01125&CFID=337
6245&CFTOKEN=35600876

David

Remove no and spam for a personal reply

On Sat, 4 Dec 2004 16:33:14 +0000, David Pocock
wrote:

I realise this is a big ask but if anyone has the time and knowledge I
would be very interested to hear from them. It is the EMV 1125 meter and
there is a two page data sheet available from this page.

http://www.lascarelectronics.com/pro...01125&CFID=337
6245&CFTOKEN=35600876

===============================

You're going to need some really expert help with this. The EMV1125
is a generic digital panel meter which has been designed to do many
different things depending on how it is connected. There is an
example in the application notes of how to hook it up to a current
shunt but it is very sketchy (lacking in details), and it looks like
additional external components are required if I'm reading it
correctly. I'd advise calling their support number and explain the
specifics of your application. One thing you need to know in advance
is the millivolts per amp rating of your current shunt. The
calibration of the EMV1125 will have to be adjusted to that number in
order to get an accurate reading.

Chuck

This looks very helpful. I will do as you suggest and check this advice
with Lascar. It is not immediately obvious to me which other of their
products can be used for my purposes. (None has the name "digital
ammeter").

Thanks for taking the time.

David

Hello David,

Based on the data sheet, the EMV 1125 is a general purpose panel meter
that the user configures for specialized applications.

It can be used to measure voltage (see the illustration at the bottom
left of the second page) but it is not really what you want. These GP
digital panel meters come in two flavors: those that will work from the
same power source they are measuring, and those that require a power
source independent of that being measured. The EMV 1125 is the latter
type, unfortunately.

To make this work, the simplest solution would be for you to connect a
9 volt battery (preferrably alkaline) to the two terminals marked
Supply Voltage, observing plus and minus polarity. (The garden variety
digital voltmeter actually works this way).

Next, connect the two terminals on the right-hand side of the board
across the shunt. One wire to each side of the shunt. The minus
terminal on the board should go to one side of the shunt and the plus
to the other side. If you mix them up, the meter will simply display a
minus sign in front of the reading. If that happens, just switch the
wires. Depending on where the shunt is located in your boat's wiring,
you might actually want both positive and negative readings, depending
on which way the current is flowing through the shunt.

It appears that the ten wires on the board relate to the ten
corresponding terminals on the meter itself. They appear to be
color-coded. 0,1,and 2 should be connected from the board to the meter.
3,4, and 5 seem not to be required. Choose which of the decimal point
positions best suits your shunt. You want to be able to display full
shunt voltage (maximum current) on the meter. Suppose you need to be
able to measure up to 199.9 millivolts. Then you would connect the
violet wire from the meter to pin six on the board (DPCOM). Tape the
ends of the unused wires.

If you'd like to verify this with Lascar, I noticed a Technical Support
page where you can just cut and paste this.

The obvious downside to this solution is that you need to use a 9-volt
battery. You could put a push-button switch in series with the positive
lead to the 9-volt battery and thus read current only when the button
was pushed. The 9-volt battery would last for years with that kind of
usage.

The next simplest approach is to return the device and choose one that
does not require an independent power source.

The last, and potentially most difficult, solution is to locate a dc-dc
converter that will provide 12 vdc to power the meter that is isolated
from the 12 vdc of your boat battery. Probably not worth the bother.

The 9-volt battery solution is really quite straightforward and you
should experience no difficulties. Let me know if you have any further
questions.


Chuck







David Pocock wrote:
I've joined this newsgroup to try to get some help on a particular
problem. I decided as a winter project on the boat to replace analogue
voltmeter and ammeter with digital ones from Lascar. I was recommended
these as being suitable and ordered them from the website:
http//:www.lascarelectronics.com
They have now arrived. No problem with wiring in the voltmeter but I
am stuck over how to wire in the milli-volt meter in a way that it
can be used to measure amps in my 12 volt circuit. I understood it
could be used to measure voltage difference on either side of a 0.1
ohm shunt to give a value in amps. This may well be the case but the
fact it comes with ten wires, a small circuit board and four extra
resistors was a bit of a shocker to someone like me who just about
knows the difference between amps, volts and watts.
I realise this is a big ask but if anyone has the time and knowledge
I would be very interested to hear from them. It is the EMV 1125
meter and there is a two page data sheet available from this page.

http://www.lascarelectronics.com/products.cfm?STOCKNO=EMV%201125&CFID=337
6245&CFTOKEN=35600876
David
Remove no and spam for a personal reply

--