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Shunt resistor, what value should i expect when solder on PCB?
Clash Royale CLAN TAG#URR8PPP
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I am using a 10mOhm 1% shunt to measure current via voltage drop.
My circuit is on a breadboard...
It behaves as if the shunt has value of ~30-40mOhm instead of 10mOhms.
I double checked this by sourcing current through the shunt alone and reading the voltage drop.
I am pretty sure the source of this extra resistance is from the contact connections to the shunt.
Right now the breadboard circuit is trimmed for a ~30-40mOhm shunt value. My question is should expect to see the correct 10mOhm value when everything solder to a PCB?
If so I need to change up the part selection and PCB component labels.
However, if i should be seeing minimal added resistance from the breadboard connections this could mean they sent me the wrong shunt value or its defective. I only have 1 unfortunately so I can verify if its behaving unexpectedly.
Here are some pictures:
Schematic, Isense+/- connect to the shunt resistor.
Resistance measurement with meter. This is showing 220mOhm, depending on what connectors I use I typical get ~40-50mOhms... the point is its definitely not 10mOhms:
Heres the breadboard bird nest. Its tuned for ~30mOhm shunt. Works accurately and consistently.
Here is the proposed PCB layout. The different ground planes are connected at a star so don't worry about that; I found it was the cleanest way to do it, I don't want to get into a ground plane argument...
connector resistance soldering shunt
asked 1 hour ago
Tony
1527
 |Â
show 1 more comment
up vote
4
down vote
favorite
I am using a 10mOhm 1% shunt to measure current via voltage drop.
My circuit is on a breadboard...
It behaves as if the shunt has value of ~30-40mOhm instead of 10mOhms.
I double checked this by sourcing current through the shunt alone and reading the voltage drop.
I am pretty sure the source of this extra resistance is from the contact connections to the shunt.
Right now the breadboard circuit is trimmed for a ~30-40mOhm shunt value. My question is should expect to see the correct 10mOhm value when everything solder to a PCB?
If so I need to change up the part selection and PCB component labels.
However, if i should be seeing minimal added resistance from the breadboard connections this could mean they sent me the wrong shunt value or its defective. I only have 1 unfortunately so I can verify if its behaving unexpectedly.
Here are some pictures:
Schematic, Isense+/- connect to the shunt resistor.
Resistance measurement with meter. This is showing 220mOhm, depending on what connectors I use I typical get ~40-50mOhms... the point is its definitely not 10mOhms:
Heres the breadboard bird nest. Its tuned for ~30mOhm shunt. Works accurately and consistently.
Here is the proposed PCB layout. The different ground planes are connected at a star so don't worry about that; I found it was the cleanest way to do it, I don't want to get into a ground plane argument...
connector resistance soldering shunt
asked 1 hour ago
Tony
1527
Get a stripboard and try it out
– PlasmaHH
1 hour ago
1
You have to learn about kelvin connection. Neither a PCB can solve the wrong way of your measuring method.
– Marko BurÅ¡iÄÂ
1 hour ago
Can you post a picture of your setup, and a schematic?
– Vladimir Cravero
1 hour ago
1
Use a 4 point shunt to have a correct measurement
– Damien
1 hour ago
2
The "kelvin connection" mentioned by Marko and the "4 point shunt" mentioned by Damien are referring to the same thing by the way. A resistor with four connections, two for current and two for voltage, so the contact resistances don't affect the measurement.
– Jack B
1 hour ago
 |Â
show 1 more comment
up vote
4
down vote
favorite
up vote
4
down vote
favorite
I am using a 10mOhm 1% shunt to measure current via voltage drop.
My circuit is on a breadboard...
It behaves as if the shunt has value of ~30-40mOhm instead of 10mOhms.
I double checked this by sourcing current through the shunt alone and reading the voltage drop.
I am pretty sure the source of this extra resistance is from the contact connections to the shunt.
Right now the breadboard circuit is trimmed for a ~30-40mOhm shunt value. My question is should expect to see the correct 10mOhm value when everything solder to a PCB?
If so I need to change up the part selection and PCB component labels.
However, if i should be seeing minimal added resistance from the breadboard connections this could mean they sent me the wrong shunt value or its defective. I only have 1 unfortunately so I can verify if its behaving unexpectedly.
Here are some pictures:
Schematic, Isense+/- connect to the shunt resistor.
Resistance measurement with meter. This is showing 220mOhm, depending on what connectors I use I typical get ~40-50mOhms... the point is its definitely not 10mOhms:
Heres the breadboard bird nest. Its tuned for ~30mOhm shunt. Works accurately and consistently.
Here is the proposed PCB layout. The different ground planes are connected at a star so don't worry about that; I found it was the cleanest way to do it, I don't want to get into a ground plane argument...
connector resistance soldering shunt
asked 1 hour ago
Tony
1527
I am using a 10mOhm 1% shunt to measure current via voltage drop.
My circuit is on a breadboard...
It behaves as if the shunt has value of ~30-40mOhm instead of 10mOhms.
I double checked this by sourcing current through the shunt alone and reading the voltage drop.
I am pretty sure the source of this extra resistance is from the contact connections to the shunt.
Right now the breadboard circuit is trimmed for a ~30-40mOhm shunt value. My question is should expect to see the correct 10mOhm value when everything solder to a PCB?
If so I need to change up the part selection and PCB component labels.
However, if i should be seeing minimal added resistance from the breadboard connections this could mean they sent me the wrong shunt value or its defective. I only have 1 unfortunately so I can verify if its behaving unexpectedly.
Here are some pictures:
Schematic, Isense+/- connect to the shunt resistor.
Resistance measurement with meter. This is showing 220mOhm, depending on what connectors I use I typical get ~40-50mOhms... the point is its definitely not 10mOhms:
Heres the breadboard bird nest. Its tuned for ~30mOhm shunt. Works accurately and consistently.
Here is the proposed PCB layout. The different ground planes are connected at a star so don't worry about that; I found it was the cleanest way to do it, I don't want to get into a ground plane argument...
connector resistance soldering shunt
connector resistance soldering shunt
asked 1 hour ago
Tony
1527
asked 1 hour ago
Tony
1527
edited 19 mins ago
asked 1 hour ago
Tony
1527
asked 1 hour ago
Tony
1527
asked 1 hour ago
Tony
1527
1527
Get a stripboard and try it out
– PlasmaHH
1 hour ago
1
You have to learn about kelvin connection. Neither a PCB can solve the wrong way of your measuring method.
– Marko BurÅ¡iÄÂ
1 hour ago
Can you post a picture of your setup, and a schematic?
– Vladimir Cravero
1 hour ago
1
Use a 4 point shunt to have a correct measurement
– Damien
1 hour ago
2
The "kelvin connection" mentioned by Marko and the "4 point shunt" mentioned by Damien are referring to the same thing by the way. A resistor with four connections, two for current and two for voltage, so the contact resistances don't affect the measurement.
– Jack B
1 hour ago
 |Â
show 1 more comment
Get a stripboard and try it out
– PlasmaHH
1 hour ago
1
You have to learn about kelvin connection. Neither a PCB can solve the wrong way of your measuring method.
– Marko BurÅ¡iÄÂ
1 hour ago
Can you post a picture of your setup, and a schematic?
– Vladimir Cravero
1 hour ago
1
Use a 4 point shunt to have a correct measurement
– Damien
1 hour ago
2
The "kelvin connection" mentioned by Marko and the "4 point shunt" mentioned by Damien are referring to the same thing by the way. A resistor with four connections, two for current and two for voltage, so the contact resistances don't affect the measurement.
– Jack B
1 hour ago
Get a stripboard and try it out
– PlasmaHH
1 hour ago
Get a stripboard and try it out
– PlasmaHH
1 hour ago
1
1
You have to learn about kelvin connection. Neither a PCB can solve the wrong way of your measuring method.
– Marko BurÅ¡iÄÂ
1 hour ago
You have to learn about kelvin connection. Neither a PCB can solve the wrong way of your measuring method.
– Marko BurÅ¡iÄÂ
1 hour ago
Can you post a picture of your setup, and a schematic?
– Vladimir Cravero
1 hour ago
Can you post a picture of your setup, and a schematic?
– Vladimir Cravero
1 hour ago
1
1
Use a 4 point shunt to have a correct measurement
– Damien
1 hour ago
Use a 4 point shunt to have a correct measurement
– Damien
1 hour ago
2
2
The "kelvin connection" mentioned by Marko and the "4 point shunt" mentioned by Damien are referring to the same thing by the way. A resistor with four connections, two for current and two for voltage, so the contact resistances don't affect the measurement.
– Jack B
1 hour ago
The "kelvin connection" mentioned by Marko and the "4 point shunt" mentioned by Damien are referring to the same thing by the way. A resistor with four connections, two for current and two for voltage, so the contact resistances don't affect the measurement.
– Jack B
1 hour ago
 |Â
show 1 more comment
2 Answers
2
active
oldest
votes
up vote
6
down vote
A breadboard like that is not suitable when a few mΩ or 10s of mΩ matter.
However, you should be able to salvage your setup by using properly soldered connections for the current sense resistor. You are apparently doing a 4-wire measurement. Solder all 4 connections to the resistor off the breadboard. You can then plug the other ends of the two sense wires into the breadboard, since those carry little current.
You should also plan your PCB layout carefully. The layout of how the current is routed thru the sense resistor, and where exactly the two sense lines are connected matters. When I've done this, I've routed the main current thru the ends of the pads for the resistor normally. The sense lines were then thin traces connected to the center of the inside of the pads.
Here is a snippet of such a layout:
R1-R4 are low-value current-sense resistors. The current to be sensed flows thru the thick traces right to left. These thick traces are the same width as the resistor pads. Those are shown as solder mask openings with the white cross-hatch pattern.
The sense lines are the thin (8 mil) tracks connected to the center of the inside edge of each resistor pad. The immediate connection to the pad is on the top layer (red) in each case. After that, they are just ordinary signal lines, and can be routed as such.
And yes, this circuit worked very well.
answered 37 mins ago
Olin Lathrop
277k28331780
I added my PCB layout to the original question. I think I did what you where talking about. I made the sense lines perpendicular to the current direction so the ground return of the Hi-current will not influence the sense lines... Once I add the 4 wire resistor I think everything will be gravy.
– Tony
10 mins ago
add a comment |Â
up vote
0
down vote
Using a two leaded resistor and the plug in type proto board is always going to have issues of added resistance in the connections. You may want to consider the use of a slightly more expensive type of sense resistor that comes with four leads. These have two main leads through which the load current is routed. The other two leads are connected to the high impedance inputs of your sensing or signal conditioning circuit.
This type of resistor is available in both SMT and leaded for THRU hole applications. The picture below shows a typical SMT current shunt resistor.
(Picture Source: https://www.ept.ca/products/ultra-low-ohmic-current-sense-resistor-high-power/)
answered 22 mins ago
Michael Karas
41.7k34497
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
6
down vote
A breadboard like that is not suitable when a few mΩ or 10s of mΩ matter.
However, you should be able to salvage your setup by using properly soldered connections for the current sense resistor. You are apparently doing a 4-wire measurement. Solder all 4 connections to the resistor off the breadboard. You can then plug the other ends of the two sense wires into the breadboard, since those carry little current.
You should also plan your PCB layout carefully. The layout of how the current is routed thru the sense resistor, and where exactly the two sense lines are connected matters. When I've done this, I've routed the main current thru the ends of the pads for the resistor normally. The sense lines were then thin traces connected to the center of the inside of the pads.
Here is a snippet of such a layout:
R1-R4 are low-value current-sense resistors. The current to be sensed flows thru the thick traces right to left. These thick traces are the same width as the resistor pads. Those are shown as solder mask openings with the white cross-hatch pattern.
The sense lines are the thin (8 mil) tracks connected to the center of the inside edge of each resistor pad. The immediate connection to the pad is on the top layer (red) in each case. After that, they are just ordinary signal lines, and can be routed as such.
And yes, this circuit worked very well.
answered 37 mins ago
Olin Lathrop
277k28331780
I added my PCB layout to the original question. I think I did what you where talking about. I made the sense lines perpendicular to the current direction so the ground return of the Hi-current will not influence the sense lines... Once I add the 4 wire resistor I think everything will be gravy.
– Tony
10 mins ago
add a comment |Â
up vote
6
down vote
A breadboard like that is not suitable when a few mΩ or 10s of mΩ matter.
However, you should be able to salvage your setup by using properly soldered connections for the current sense resistor. You are apparently doing a 4-wire measurement. Solder all 4 connections to the resistor off the breadboard. You can then plug the other ends of the two sense wires into the breadboard, since those carry little current.
You should also plan your PCB layout carefully. The layout of how the current is routed thru the sense resistor, and where exactly the two sense lines are connected matters. When I've done this, I've routed the main current thru the ends of the pads for the resistor normally. The sense lines were then thin traces connected to the center of the inside of the pads.
Here is a snippet of such a layout:
R1-R4 are low-value current-sense resistors. The current to be sensed flows thru the thick traces right to left. These thick traces are the same width as the resistor pads. Those are shown as solder mask openings with the white cross-hatch pattern.
The sense lines are the thin (8 mil) tracks connected to the center of the inside edge of each resistor pad. The immediate connection to the pad is on the top layer (red) in each case. After that, they are just ordinary signal lines, and can be routed as such.
And yes, this circuit worked very well.
answered 37 mins ago
Olin Lathrop
277k28331780
I added my PCB layout to the original question. I think I did what you where talking about. I made the sense lines perpendicular to the current direction so the ground return of the Hi-current will not influence the sense lines... Once I add the 4 wire resistor I think everything will be gravy.
– Tony
10 mins ago
add a comment |Â
up vote
6
down vote
up vote
6
down vote
A breadboard like that is not suitable when a few mΩ or 10s of mΩ matter.
However, you should be able to salvage your setup by using properly soldered connections for the current sense resistor. You are apparently doing a 4-wire measurement. Solder all 4 connections to the resistor off the breadboard. You can then plug the other ends of the two sense wires into the breadboard, since those carry little current.
You should also plan your PCB layout carefully. The layout of how the current is routed thru the sense resistor, and where exactly the two sense lines are connected matters. When I've done this, I've routed the main current thru the ends of the pads for the resistor normally. The sense lines were then thin traces connected to the center of the inside of the pads.
Here is a snippet of such a layout:
R1-R4 are low-value current-sense resistors. The current to be sensed flows thru the thick traces right to left. These thick traces are the same width as the resistor pads. Those are shown as solder mask openings with the white cross-hatch pattern.
The sense lines are the thin (8 mil) tracks connected to the center of the inside edge of each resistor pad. The immediate connection to the pad is on the top layer (red) in each case. After that, they are just ordinary signal lines, and can be routed as such.
And yes, this circuit worked very well.
answered 37 mins ago
Olin Lathrop
277k28331780
A breadboard like that is not suitable when a few mΩ or 10s of mΩ matter.
However, you should be able to salvage your setup by using properly soldered connections for the current sense resistor. You are apparently doing a 4-wire measurement. Solder all 4 connections to the resistor off the breadboard. You can then plug the other ends of the two sense wires into the breadboard, since those carry little current.
You should also plan your PCB layout carefully. The layout of how the current is routed thru the sense resistor, and where exactly the two sense lines are connected matters. When I've done this, I've routed the main current thru the ends of the pads for the resistor normally. The sense lines were then thin traces connected to the center of the inside of the pads.
Here is a snippet of such a layout:
R1-R4 are low-value current-sense resistors. The current to be sensed flows thru the thick traces right to left. These thick traces are the same width as the resistor pads. Those are shown as solder mask openings with the white cross-hatch pattern.
The sense lines are the thin (8 mil) tracks connected to the center of the inside edge of each resistor pad. The immediate connection to the pad is on the top layer (red) in each case. After that, they are just ordinary signal lines, and can be routed as such.
And yes, this circuit worked very well.
answered 37 mins ago
Olin Lathrop
277k28331780
edited 23 mins ago
answered 37 mins ago
Olin Lathrop
277k28331780
answered 37 mins ago
Olin Lathrop
277k28331780
answered 37 mins ago
Olin Lathrop
277k28331780
277k28331780
I added my PCB layout to the original question. I think I did what you where talking about. I made the sense lines perpendicular to the current direction so the ground return of the Hi-current will not influence the sense lines... Once I add the 4 wire resistor I think everything will be gravy.
– Tony
10 mins ago
add a comment |Â
I added my PCB layout to the original question. I think I did what you where talking about. I made the sense lines perpendicular to the current direction so the ground return of the Hi-current will not influence the sense lines... Once I add the 4 wire resistor I think everything will be gravy.
– Tony
10 mins ago
I added my PCB layout to the original question. I think I did what you where talking about. I made the sense lines perpendicular to the current direction so the ground return of the Hi-current will not influence the sense lines... Once I add the 4 wire resistor I think everything will be gravy.
– Tony
10 mins ago
I added my PCB layout to the original question. I think I did what you where talking about. I made the sense lines perpendicular to the current direction so the ground return of the Hi-current will not influence the sense lines... Once I add the 4 wire resistor I think everything will be gravy.
– Tony
10 mins ago
add a comment |Â
up vote
0
down vote
Using a two leaded resistor and the plug in type proto board is always going to have issues of added resistance in the connections. You may want to consider the use of a slightly more expensive type of sense resistor that comes with four leads. These have two main leads through which the load current is routed. The other two leads are connected to the high impedance inputs of your sensing or signal conditioning circuit.
This type of resistor is available in both SMT and leaded for THRU hole applications. The picture below shows a typical SMT current shunt resistor.
(Picture Source: https://www.ept.ca/products/ultra-low-ohmic-current-sense-resistor-high-power/)
answered 22 mins ago
Michael Karas
41.7k34497
add a comment |Â
up vote
0
down vote
Using a two leaded resistor and the plug in type proto board is always going to have issues of added resistance in the connections. You may want to consider the use of a slightly more expensive type of sense resistor that comes with four leads. These have two main leads through which the load current is routed. The other two leads are connected to the high impedance inputs of your sensing or signal conditioning circuit.
This type of resistor is available in both SMT and leaded for THRU hole applications. The picture below shows a typical SMT current shunt resistor.
(Picture Source: https://www.ept.ca/products/ultra-low-ohmic-current-sense-resistor-high-power/)
answered 22 mins ago
Michael Karas
41.7k34497
add a comment |Â
up vote
0
down vote
up vote
0
down vote
Using a two leaded resistor and the plug in type proto board is always going to have issues of added resistance in the connections. You may want to consider the use of a slightly more expensive type of sense resistor that comes with four leads. These have two main leads through which the load current is routed. The other two leads are connected to the high impedance inputs of your sensing or signal conditioning circuit.
This type of resistor is available in both SMT and leaded for THRU hole applications. The picture below shows a typical SMT current shunt resistor.
(Picture Source: https://www.ept.ca/products/ultra-low-ohmic-current-sense-resistor-high-power/)
answered 22 mins ago
Michael Karas
41.7k34497
Using a two leaded resistor and the plug in type proto board is always going to have issues of added resistance in the connections. You may want to consider the use of a slightly more expensive type of sense resistor that comes with four leads. These have two main leads through which the load current is routed. The other two leads are connected to the high impedance inputs of your sensing or signal conditioning circuit.
This type of resistor is available in both SMT and leaded for THRU hole applications. The picture below shows a typical SMT current shunt resistor.
(Picture Source: https://www.ept.ca/products/ultra-low-ohmic-current-sense-resistor-high-power/)
answered 22 mins ago
Michael Karas
41.7k34497
answered 22 mins ago
Michael Karas
41.7k34497
answered 22 mins ago
Michael Karas
41.7k34497
answered 22 mins ago
Michael Karas
41.7k34497
41.7k34497
add a comment |Â
add a comment |Â
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Get a stripboard and try it out
– PlasmaHH
1 hour ago
1
You have to learn about kelvin connection. Neither a PCB can solve the wrong way of your measuring method.
– Marko BurÅ¡iÄÂ
1 hour ago
Can you post a picture of your setup, and a schematic?
– Vladimir Cravero
1 hour ago
1
Use a 4 point shunt to have a correct measurement
– Damien
1 hour ago
2
The "kelvin connection" mentioned by Marko and the "4 point shunt" mentioned by Damien are referring to the same thing by the way. A resistor with four connections, two for current and two for voltage, so the contact resistances don't affect the measurement.
– Jack B
1 hour ago