34330A 30 A Current Shunt any cheaper alternative?

[Myauk]

Hello All,

While working on certain test system, I needed to measure current
value up to 4A.

As I looked for the DMM with GPIB cable that supports the measurement
up to 4A, I could not find any.

Agilent suggests me to use 34330A 30 A Current Shunt which is so
expensive after adding the calibration cost. (around 600 Sing$).

Is there anyone who has some experience in such DMMs with GPIB cables?

Could anyone please suggest me a cheaper alternative for 34330A 30 A
Current Shunt?

I know that I can design a shunt by myself, however, I would prefer to
buy a ready-made shunt to save time.

Best Regards

 

[Bill Sloman]

Hello All,

While working on certain test system, I needed to measure current
value up to 4A.

As I looked for the DMM with GPIB cable that supports the measurement
up to 4A, I could not find any.

Agilent suggests me to use 34330A 30 A Current Shunt which is so
expensive after adding the calibration cost. (around 600 Sing$).

Is there anyone who has some experience in such DMMs with GPIB cables?

Could anyone please suggest me a cheaper alternative for 34330A 30 A
Current Shunt?

I know that I can design a shunt by myself, however, I would prefer to
buy a ready-made shunt to save time.

Farnell offers a couple of 60A shunts for about 40 euro - roughly 80
Singapore dillars. They also offer a wide variety of "low Ohmic value" and
"power metal strip" resistors, with values down to 1milliohm and tolerances
as a good as +/-1% at prices that run aound one euro/two Singapore dollars -
but the minimum order qunatity is a least five.

 

[Tim Shoppa]

Hello All,

While working on certain test system, I needed to measure current
value up to 4A.

As I looked for the DMM with GPIB cable that supports the measurement
up to 4A, I could not find any.

Agilent suggests me to use 34330A 30 A Current Shunt which is so
expensive after adding the calibration cost. (around 600 Sing$).

Is there anyone who has some experience in such DMMs with GPIB cables?

Could anyone please suggest me a cheaper alternative for 34330A 30 A
Current Shunt?

I know that I can design a shunt by myself, however, I would prefer to
buy a ready-made shunt to save time.

Best Regards

Some of us don't call them shunts, we call them power resistors. Heck,
often they're just pieces of resistance wire. Back in the good old
days, when men were REAL men, women were REAL women, and small fuzzy
creatures from Alpha Centauri were REAL small fuzzy creatures from
Alpha Centauri, we all took basic meter movements and use resistors to
get the voltage or current measurement range we actually needed.

If you put 4A through a 0.05 ohm resistor, you have a 0.2V drop across
the resistor. So with a DMM set to 200mV full scale you see 1A as
50mV, 2A as 100mV, 3A as 150mV, 4A as 200mV, etc.

If you need less voltage drop across the shunt, you use a lower-ohm
resistor. Also look at power dissipation. Putting 4A through a 1/4
watt 0.1 ohm resistor won't work for very long!

Some manufacturers call these small ohmic values "current sense"
resistors. Some, especially the milliohm values, are available as "4-
wire" configurations to remove the error caused by the resistor lead
voltage drops.

I don't know about Singapore, but here in the US these are standard
stock items at Mouser and Digikey etc.

Tim.

 

[[email protected]]

Hello All,

While working on certain test system, I needed to measure current
value up to 4A.

As I looked for the DMM with GPIB cable that supports the measurement
up to 4A, I could not find any.

Agilent suggests me to use 34330A 30 A Current Shunt which is so
expensive after adding the calibration cost. (around 600 Sing$).

Is there anyone who has some experience in such DMMs with GPIB cables?

Could anyone please suggest me a cheaper alternative for 34330A 30 A
Current Shunt?

I know that I can design a shunt by myself, however, I would prefer to
buy a ready-made shunt to save time.

Best Regards

I'll echo what everyone else says. www.digikey.com - search for
"resistor", then look at the category for either current sense or
wirewound resistors. Then look for the appropriate power rating.
Between 2W and 10W, both categories list a bunch of parts for between
$2 and $20.

Chris

 

[Spehro Pefhany]

I'll echo what everyone else says. www.digikey.com - search for
"resistor", then look at the category for either current sense or
wirewound resistors. Then look for the appropriate power rating.
Between 2W and 10W, both categories list a bunch of parts for between
$2 and $20.

Chris

Here's one for about $30 USD

http://www.murata-ps.com/data/meters/dpm_shunts.pdf

Murata should be easily available in Singapore.

 

[[email protected]]

Hello All,

While working on certain test system, I needed to measure current
value up to 4A.

As I looked for the DMM with GPIB cable that supports the measurement
up to 4A, I could not find any.

Agilent suggests me to use 34330A 30 A Current Shunt which is so
expensive after adding the calibration cost. (around 600 Sing$).

Is there anyone who has some experience in such DMMs with GPIB cables?

Could anyone please suggest me a cheaper alternative for 34330A 30 A
Current Shunt?

I know that I can design a shunt by myself, however, I would prefer to
buy a ready-made shunt to save time.

Best Regards

I've used a few off Ebay item number 350138498285 (China) . Very nice
50A shunts at $20 USD. They also throw in a panel DVM for free. (not
GPIB though).

 

[Myauk]

Some of us don't call them shunts, we call them power resistors. Heck,
often they're just pieces of resistance wire. Back in the good old
days, when men were REAL men, women were REAL women, and small fuzzy
creatures from Alpha Centauri were REAL small fuzzy creatures from
Alpha Centauri, we all took basic meter movements and use resistors to
get the voltage or current measurement range we actually needed.

If you put 4A through a 0.05 ohm resistor, you have a 0.2V drop across
the resistor. So with a DMM set to 200mV full scale you see 1A as
50mV, 2A as 100mV, 3A as 150mV, 4A as 200mV, etc.

If you need less voltage drop across the shunt, you use a lower-ohm
resistor. Also look at power dissipation. Putting 4A through a 1/4
watt 0.1 ohm resistor won't work for very long!

Some manufacturers call these small ohmic values "current sense"
resistors. Some, especially the milliohm values, are available as "4-
wire" configurations to remove the error caused by the resistor lead
voltage drops.

I don't know about Singapore, but here in the US these are standard
stock items at Mouser and Digikey etc.

Tim.

I know, but, what I don't know is why Agilent is asking so much money
around 300 S$ for calibration!

What is it so special in agilent 34330A ?

Is it because it is an Agilent product?



Regards

 

[Myauk]

I know, but, what I don't know is why Agilent is asking so much money
around 300 S$ for calibration!

What is it so special in agilent 34330A ?

Is it because it is an Agilent product?



Regards

The reason might be tolerance at that resistance value, it think.

 

[Spehro Pefhany]

I know, but, what I don't know is why Agilent is asking so much money
around 300 S$ for calibration!

Because if you really need the paperwork (certificate) you'll pay for
it. It costs money to run a NIST-tracable metrology lab, and many
people don't need the certificate.

With inexpensive stuff it may be cheaper to throw it away at the end
of the calibration interval. Certainly that is the case with
mechanical gage blocks.

What is it so special in agilent 34330A ?

Is it because it is an Agilent product?



Regards

You've probably already spent more $ worth of time than it's worth at
the overheaded cost of a good test engineer, assuming you only need
one.

Anyway, the list price from Agilent (also Allied, Newark etc.) for the
34330A 30A 0.3% shunt is only $81 USD, which is less than $120 SGD.
Pretty reasonable, considering it has a housing and four bananna
plugs/jacks, and is from a generally reputable manufacturer.


Best regards,
Spehro Pefhany

 

[[email protected]]

I've used a few off Ebay item number  350138498285 (China) . Very nice
50A shunts at $20 USD. They also throw in a  panel DVM for free. (not
GPIB though).

Also they are very common swap meet items.

I'm not sure I'd be using a wirewound device. The shunts I have look
like a piece of copper mounted on an insulator and set up for 4
terminal (Kelvin) measurement.

 

[Spehro Pefhany]

Also they are very common swap meet items.

I'm not sure I'd be using a wirewound device. The shunts I have look
like a piece of copper mounted on an insulator and set up for 4
terminal (Kelvin) measurement.

They should be a low tempco alloy (eg. Manganin) and they should be
made to be fairly non-inductive. Copper has a high tempco (like most
elemental metals) of around +3900ppm/K at room temperature.


Best regards,
Spehro Pefhany

 

[Winfield Hill]

Also they are very common swap meet items.

I'm not sure I'd be using a wirewound device. The shunts I have
look like a piece of copper mounted on an insulator and set up
for 4 terminal (Kelvin) measurement.

Two large copper blocks, with screw terminals, are
the dominant features of shunts. The resistance
element is manganin, which has zero resistance
tempco. http://en.wikipedia.org/wiki/Manganin
http://www.lakeshore.com/temp/acc/am_wirets.html
http://nvl.nist.gov/pub/nistpubs/sp958-lide/063-065.pdf
http://www.cshunt.com/pdf/page1.pdf

The large copper blocks, and the user's heavy copper
current-carrying wire are important for heat removal
from the manganin element. A common power resistor,
even if equipped with Kelvin terminals, cannot match
the performance of a shunt.

I use Empro shunts, http://www.emproshunts.com/
http://www.electro-meters.com/Empro/Empro.htm

 

[Spehro Pefhany]

Two large copper blocks, with screw terminals, are
the dominant features of shunts. The resistance
element is manganin, which has zero resistance
tempco. http://en.wikipedia.org/wiki/Manganin
http://www.lakeshore.com/temp/acc/am_wirets.html
http://nvl.nist.gov/pub/nistpubs/sp958-lide/063-065.pdf
http://www.cshunt.com/pdf/page1.pdf

The large copper blocks, and the user's heavy copper
current-carrying wire are important for heat removal
from the manganin element. A common power resistor,
even if equipped with Kelvin terminals, cannot match
the performance of a shunt.

I use Empro shunts, http://www.emproshunts.com/
http://www.electro-meters.com/Empro/Empro.htm

Yes, I have used a whack of 15kA shunts (and some smaller ones) like
those in a plating installation.

The large copper blocks/heatsink fins/water cooling is/are probably a
bit excessive for the OP's application, which would likely only
involve dissipating 0.160W maximum. ((4A)^2 * 0.01 ohms).

Here's another supplier-- this one goes down to 5A/50mV.

http://www.cshunt.com/dc_ammeter_shunts.html


Best regards,
Spehro Pefhany

 

[Glen Walpert]

Two large copper blocks, with screw terminals, are
the dominant features of shunts. The resistance
element is manganin, which has zero resistance
tempco. http://en.wikipedia.org/wiki/Manganin
http://www.lakeshore.com/temp/acc/am_wirets.html
http://nvl.nist.gov/pub/nistpubs/sp958-lide/063-065.pdf
http://www.cshunt.com/pdf/page1.pdf

The Wikipedia article claims that Manganin has "virtually zero
temperature coefficient of resistance value" - true, but only within a
small temperature range. Only your last reference provides a
resistance vs temperature curve for their specific alloy of manganin;
some other manganin alloys are significantly worse and they all have
exactly zero tempco only at one specific temperature.

Some interesting details on resistance alloys can be found in the ASM
Metals Handbook vol 2, Nonferrous Appoys and Special Purpose
Materials, in the Electrical Resistance Alloys section, including
curves for a number of alloys showing the variation of a 75Ni-20Cr-3Al
alloy to be about an order of magnitude less than the best manganin.

 

[[email protected]]

They should be a low tempco alloy (eg. Manganin) and they should be
made to be fairly non-inductive. Copper has a high tempco (like most
elemental metals) of around +3900ppm/K at room temperature.

Best regards,
Spehro Pefhany

You have a point. Probably an alloy since it didn't have a weathered
look of copper.