Riedon Inc.

300 Cypress Avenue

Alhambra CA 91801

(626) 284-9901

(626) 284-1704

08/16

www.riedon.com

RS Series

Precision Current / DC Current Shunts

TECHNICAL NOTES

Mounting: Shunts should be mounted with manganin resistive blades in a vertical position in order to

promote the free convectional flow of air. If vertical mounting is not practical, forced air cooling or adding

heat sinks to the blocks can reduce the operating temperature. The manganin blades must never exceed

+145°C, otherwise permanent resistance change may occur.

When current of 100A or greater is passing through the shunt, the major portion of heat generated is dis-

sipated by conduction through the shunt terminal blocks into the connecting buss bar or cable. Therefore

it is necessary to insure that good contact is made between the shunt terminal blocks and the conductor

terminals and that the conductors have adequate cross section to keep the temperature of the shunt from

exceeding 145°C ( 125°C recommended ).

If the shunt is mounted in an enclosure, care must be taken to ensure adequate cooling. If the power density

is greater than 1/4 watt per square inch of the enclosure surface for all enclosed devices, additional cooling

must be supplied in the form of air vents or fans.

Shunts also must be installed in a way that protects them from thermal expansion forces produced from

buss bar or short-circuit forces. Flexible wiring may be required in high pulse current, high vibration, or high

temperature applications.

Where possible, all shunts should be mounted on the ground side of the circuit. For circuits above 750VDC,

RS shunts must be mounted on the ground side due to the dielectric strength of the shunt base.

Output Voltage

Current

Current

Mounting Orientation

UP

Operating Current Derating: For continuous operation, it is recommended that shunts are not run at more

than two thirds (2/3) the rated current under normal conditions per IEEE standards for DC instrument shunts.

At ambient temperatures above 40°C, the current must be further derated to prevent damage.

Pulse Operation: Shunts that do not need continuous operation and are only exposed to intermittent pulses

can be operated at levels above their rated current for short periods of times. Pulses are limited to the

maximum temperature of the blades not exceeding 145°C ( 125°C recommended ). Many variables such as

ambient temperature, cross section of the current carrying conductors, and pulse duration make calculating

exact values difficult. Shunt size will need to be validated by customer for pulse current and duty cycle on a

case by case basis.