Guidelines for Setting Resistance Test Thresholds

Among other things, cable testers are used to ensure 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).
1goodconn   short-example


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.

 

go-nogo-graphic


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.

adjustable-graphic

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 click here.

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 click here.


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. Click here for more information on HV insulation testing. A low voltage specification for Insulation Resistance is not important when HV tests 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.

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
1000HX .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
CH2 .1 - 1M Ω .001 - 100Ω N/A 5MΩ - 1GΩ Resistors
Diodes
Capacitors
Twisted Pairs
Easy Touch .1 - 100KΩ .001 - 10Ω
2nd Qtr. 2011
5MΩ 5MΩ - 1GΩ Resistors
Diodes
Capacitors
Twisted Pairs
LED's
Zener Diodes