- #1
Junior01
I need to measure current in DC system. I have circuit breaker (125A), so 150A shunt is selected. On that shunt ammeter is connected. But that ammeter has 60mV, scale 0-150A. What does this 60mV means on ammeter? Is it correct?
Understanding Shunt Selection for Accurate Current Measurement in DC Systems
In summary, in order to measure current in a DC system, a shunt is necessary. The shunt will cause a small voltage drop, which is proportional to the current passing through it. A 150A/60mV shunt is recommended for this purpose. The ammeter will read the voltage drop and display it on a scale, which can be adjusted by selecting a proper shunt. When selecting a shunt, it is important to make sure that the ammeter's full-scale deflection and the shunt's mV rating are the same. It is also important to consider the measuring range of the ammeter, as some may require an external shunt for higher currents. The size and orientation of the ammeter can
- #2
Baarken
See this: http://www.exalto.com/en-us/vdo-vl-ammeter-shunt-150a-60mv-single-a2c59514047
From the link:
So if you measure 0 V that means 0 A and if you measure 60 mV that means you have 150 A.
From the link:
So if you measure 0 V that means 0 A and if you measure 60 mV that means you have 150 A.
- #3
Junior01
Thank you, but what is measuring range then. The instruments (Deif) has measuring range 1mA...40A, but on my instrument scale is 0-150A? What is different between scale and mesuring range?
- #4
Baarken
Take a look at this video and see if it is of any help.
Last edited by a moderator:
- #5
Junior01
Thank you, but I really have no idea how to select proper ammeter.
Here is a datasheet od Deif instruments, on page 4. I have DC instruments and there is measuring range from 1mA-50A, there is no 150A. So, how my instrument will show on scale 150A, if measuring range is up to 50A.
https://www.deif.com/products/eq#documentation
Here is a datasheet od Deif instruments, on page 4. I have DC instruments and there is measuring range from 1mA-50A, there is no 150A. So, how my instrument will show on scale 150A, if measuring range is up to 50A.
https://www.deif.com/products/eq#documentation
- #6
cnh1995
Homework Helper
Gold Member
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When you select a shunt, there is a multiplying factor for that shunt which gives you the actual value of the current. If your ammeter's full-scale deflection is 50A and you have extended its range to 150A (using shunt), multiplying factor would be 3. This means when your meter is showing 50A (full scale deflection), the actual current is 150A.Junior01 said:
- #7
- #8
Baarken
You need an ammeter.
What I think is confusing for you is that the ammeter reads a voltage drop across the shunt, which is proportional to the current through the shunt, which is seen from Ohm's law.
Look at the circuit below, the resistance is your shunt device.
If you have a ammeter with a scale of 0-50 A, but your shunt can measure 0-150 A then do as described in post #6, but make sure the mV rating is the same for your ammeter and shunt (60 mV).
What I think is confusing for you is that the ammeter reads a voltage drop across the shunt, which is proportional to the current through the shunt, which is seen from Ohm's law.
Look at the circuit below, the resistance is your shunt device.
If you have a ammeter with a scale of 0-50 A, but your shunt can measure 0-150 A then do as described in post #6, but make sure the mV rating is the same for your ammeter and shunt (60 mV).
- #9
Junior01
Thank you.
But, my problem is that I don't know what measuring range means (attached datasheet or picture in post #7). There is 1mA-50A, it's probably not scale, because scale is changable?
But, my problem is that I don't know what measuring range means (attached datasheet or picture in post #7). There is 1mA-50A, it's probably not scale, because scale is changable?
- #10
Baarken
Aha, I think that the measuring ranges from datasheet in post #7 is the range the display can measure without having to use an external shunt. If you wish to go above, you need an external shunt.
See this link:
http://www.wpa.ie/Products/ProcessIndicators/AnalogMetersIndicators.aspx
They write:
Maybe @jim hardy hardy can help us to put an end to this.
See this link:
http://www.wpa.ie/Products/ProcessIndicators/AnalogMetersIndicators.aspx
They write:
Maybe @jim hardy hardy can help us to put an end to this.
- #11
jim hardy
Science Advisor
Gold Member
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c'mon guys, this isn't an electrical problem it's a catalog reading problem.
You know how an ammeter with a shunt works.
So you need a shunt that measures 150 amps. Looks like those come in two flavors - 60 mv and 150 mv. SO you need a meter that shows full scale at whichever millivolts you pick for your shunt.
60 mv looks like a good choice
Delf's ordering looks painless enough
.............................So pick a meter the size you want. And note you can choose 90 degree or 270 degree needle travel...
if you want the smallest size meter i'd guess it's the second one
bigger sizes are further down the table.
figure out how to specify 60mv/1ma sensitivity and scale "0 - 150 Amps"
1 ma input(measuring range) and specify scale --- 150 DC amps ?
Observe note 4 on the catalog page - you'll want to mount it within one meter of the shunt or else order special longer leads...
if that creates a problem it's worth a call to their sales rep.
Focus guys, focus.
You know how an ammeter with a shunt works.
So you need a shunt that measures 150 amps. Looks like those come in two flavors - 60 mv and 150 mv. SO you need a meter that shows full scale at whichever millivolts you pick for your shunt.
60 mv looks like a good choice
Delf's ordering looks painless enough
.............................So pick a meter the size you want. And note you can choose 90 degree or 270 degree needle travel...
if you want the smallest size meter i'd guess it's the second one
bigger sizes are further down the table.
figure out how to specify 60mv/1ma sensitivity and scale "0 - 150 Amps"
1 ma input(measuring range) and specify scale --- 150 DC amps ?
Observe note 4 on the catalog page - you'll want to mount it within one meter of the shunt or else order special longer leads...
if that creates a problem it's worth a call to their sales rep.
Focus guys, focus.
Attachments
Last edited:
1. What is a shunt and how is it used in DC systems?
A shunt is a low-resistance device that is placed in series with a load in a DC circuit. It is used to measure the current flowing through the circuit by creating a small voltage drop that can be measured and converted to a current value using Ohm's law.
2. How is the value of a shunt selected for accurate current measurement?
The value of a shunt is selected based on the maximum expected current in the circuit. It should be low enough to minimize the voltage drop, but high enough to prevent overheating. A good rule of thumb is to select a shunt with a resistance that is 1/1000th of the maximum current in the circuit.
3. What are the factors that affect the accuracy of current measurement using a shunt?
The accuracy of current measurement using a shunt can be affected by factors such as shunt resistance, temperature, and placement in the circuit. A higher shunt resistance can result in a larger voltage drop and a less accurate measurement. Temperature can also affect the shunt's resistance, so it is important to select shunts with a low temperature coefficient. Additionally, the shunt should be placed in a location where it will not be affected by stray magnetic fields or other sources of interference.
4. How can one ensure proper shunt selection for accurate current measurement?
To ensure proper shunt selection, it is important to carefully calculate the expected current in the circuit and select a shunt with an appropriate resistance value. It is also important to consider the temperature coefficient and placement of the shunt to minimize any sources of error. Additionally, regularly calibrating the shunt and using high-quality equipment can help ensure accurate current measurement.
5. Can a shunt be used for both AC and DC current measurement?
No, a shunt is only suitable for DC current measurement. This is because AC current is constantly changing direction, which can cause errors in the measurement. For AC current measurement, other devices such as current transformers or Hall effect sensors should be used.
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