Guidelines for Setting Resistance Test Thresholds

Among other things, cable testers are used to insure that cable assemblies do not have OPENS or SHORTS. In simple terms it looks like this:

Intended connections: points that ARE intended to be connected by wires.		Not-intended connections: points, or wires, that are NOT intended to be connected, are called (SHORTS)

Cable testers measure the resistance between all test points to determine if there are, or are not connections.
The big question is; at what resistance threshold are OPENS and SHORTS detected?

Basic Go/No Go Continuity Tester

Basic continuity testers generally have one fixed threshold (the resistance is usually not very accurate and can range from 100 to 10,000 ohms). Resistances measured under this threshold are seen, while resistances measured above this threshold are not seen. Whether they are OPENS or SHORTS is determined by whether they are intended connections or not as illustrated by this graphic.

Basic continuity testers have fixed resistance measuring thresholds

Cable Testers with Selectable Resistance Thresholds

Cable testers that have variable resistance thresholds allow you to set the measured resistance value that will determine pass/fail test status as illustrated by this drawing.

To set an appropriate Connection Resistance Threshold you must first determine the nominal resistance of the wires you are testing. For help determining standard wire resistance follow this link: http://www.easy-wire.com/testing/resistance/wirecalc.html

Recommended Connection Resistance Test Settings*

Stringent Test	Good Test	Moderate Test
1.05% of Actual Resistance + .5 ohms	Greater of either 2 ohms or 1.10% of Actual Resistance + 1 ohm	Greater of either 5 ohms or 1.20% of Actual Resistance + 2 ohms

*Note: for very low resistance measurements use 4-wire Kelvin Testing. For more information on 4-wire Kelvin Testing follow this link: http://www.easy-wire.com/testing/resistance/fourwire.html

Recommended Low Voltage Insulation Resistance Test Settings*

Stringent Test	Good Test	Moderate Test
5 Meg Ohms	500K ohms	100K ohms

*Note: while a Low Voltage Insulation Resistance test does a better job of finding shorts, it is NOT as effective as HV insulation resistance testing. See http://www.easy-wire.com/testing/guidelines/voltinsl.htm for more information on HV insulation testing. A low voltage specification for Insulation Resistance is not important when HV test are performed.

Using Dual-Resistance Settings to Ignore Embedded Components
Cirris testers use dual-resistance thresholds. The lower threshold (components >) is used to verify that wires/points connected via diodes, resistors, and/or capacitors are tested for shorts. The higher threshold (IR) is used to verify that wires/points not connected to such components are tested at a more stringent LV Insulation Resistance value to all other such wires/points. For more info on testing components go here: http://www.easy-wire.com/testing/guidelines/testcomps.htm

Dual-Resistance Settings allowing testing of componets.

Dual-Resistance Settings allowing testing of componets.

Table of Cirris Testers with Adjustable Resistance Thresholds

Model	Connection Resis. Range	4-Wire Connection Resistance Range	Low Voltage Insulation Resistance MAX	High Voltage Insulation Resistance Range	Components Tested
1000RX	.1 - 10KΩ +50KΩ, 100KΩ, 500KΩ, 1MΩ, 5MΩ	N/A	5M Ω	N/A	Resistors Diodes
1100R+	.1 - 100KΩ 500KΩ, 1MΩ, 5MΩ	.005 - 10Ω	5MΩ	N/A	Resistors Diodes Capacitors
1000H+	.1 - 100KΩ 500KΩ, 1MΩ, 5MΩ	.001 - 10Ω	N/A	5MΩ - 500MΩ	Resistors Diodes Capacitors Twisted Pairs
1100H+	.1 - 100KΩ 500KΩ, 1MΩ, 5MΩ	.001 - 10Ω	5MΩ	5MΩ - 1GΩ	Resistors Diodes Capacitors Twisted Pairs
Touch 1	.1 - 100KΩ	.001 - 10Ω	5MΩ	5MΩ - 1GΩ	Resistors Diodes Capacitors Twisted Pairs LED's Zener Diodes
Easy-Wire CR	.1 - 1.0M Ω	.005 - 75Ω	100&Omega - 500KΩ	N/A	Resistors Diodes Capacitors
CH+	.1 - 100KΩ	.001 - 10Ω	N/A	5MΩ - 1GΩ	Resistors Diodes Capacitors Twisted Pairs

Cirris Systems - Technical Tips - Setting Resistance Thresholds