What is a shunt?
A shunt is simply a very precise resistor whose operation generally follows Ohm's law.
What is a current shunt resistor?
Current shunt resistors are low resistance precision resistors used to measure AC or DC electrical currents by the voltage drop those currents create across the resistance. These are also sometimes called ammeter shunts, which are a type of current sensor.
What is the best way to mount a shunt?
Ideally, shunts should be mounted such that the resistive elements are oriented in a vertical plane to promote better cooling of the elements. This means that our shunts that include a base should be mounted to a panel or wall and not a floor or ceiling.
What is the accuracy of Bourns® Shunts?
We offer a standard tolerance of ±0.25 %, however, we may be able to provide shunts with a tolerance as tight as ±0.1 % upon request.
What voltage output options are offered for your shunts?
Our shunts are offered with either 50 mV or 100 mV outputs as standard. However, we can support nearly any voltage output upon request, including 60 mV and 75 mV.
Are your shunts MIL spec?
The MK series of shunts are built to meet the standards of CID (Commercial Item Description) A-A-55524, which superseded MIL STD 91586.
What does rated current mean in regard to your shunts?
Our shunts are offered in many standard current ratings. "Current rating", often referred to as full scale, is the maximum current that a device is designed to handle or measure accurately. When applied to the shunt will result in the selected voltage output. For continuous use, we recommend that the shunt be operated at no more than 2/3 rated or full-scale current.
Why do you recommend de-rating your shunts below rated or full-scale current?
We recommend not exceeding 2/3rds of the rated or full-scale current in order to limit thermal heating of the resistive element.
What is the power rating for your shunts?
The power rating of a shunt will always adhere to Ohm's law and may be calculated using the formula P=I×V, where I is the rated current and V is the chosen millivolt output of the shunt.
Why do you recommend de-rating your shunts below rated or full-scale current?
We recommend not exceeding 2/3 rated or full-scale current in order to limit thermal heating of the resistive element.
What is the power rating for your shunts?
The power rating of a shunt will always adhere to Ohm's law and may be calculated using the formula P=I×V, where I is the rated current and V is the chosen millivolt output of the shunt.
Can shunts be used to measure short duration pulses?
Yes, a shunt can be used to measure pulses. However, there is an important consideration: it is permissible to exceed the rated current of a shunt for a short period of time. The length of time will depend entirely on thermal concerns. It is important that the resistance element of the shunt not exceed 140 °C or the resistance value will forever be altered and the shunt ruined. In order to provide an additional safety factor, we recommend that the temperature of the resistance element not exceed 125 °C. Keep in mind that the voltage output of the shunt will be proportional to the input current, so it is necessary to ensure that the input of any monitoring equipment is not exceeded.
Can shunts be used to measure AC currents as well as DC currents?
Bourns® shunts may be used to measure low frequency AC currents. There is the possibility of electrical noise at higher frequencies, however, and experience shows that the shunt will behave very well at frequencies up to about 1 kHz.
I'd like to monitor a 500-watt source, will your shunts do this?
Probably! Remember that the shunt is not measuring the power of the source, only the current it provides to the load. Determine the expected current draw and then divide the expected current draw by 2/3 or 0.666 to determine the full scale or rated current you will need. You will also need to decide if you would prefer a 50 mV or 100 mV output.