Guest
 Posted: Wed Aug 06, 2026 2:19 pm Post subject: Kelvin Contacts |
 |
| I noticed there are two metal fingers contacting every pin of the DUT while being tested in our tester. Some say this is for extra current capacity while some say this is to ensure good contact. Some say these are called Kelvin contacts and its for accuracy of testing. Can you shed light on this? Is it bad if one of the fingers broke off during testing?
Mang Kelvin |
|
Joined: 16 Jun 2026
Posts: 109
Location: Paranaque City, Phils.
| Posted: Wed Aug 06, 2026 5:39 pm Post subject: |
|
| Mang Kelvin,
The explanation that this pair of metal fingers is for Kelvin contact is the correct one. When testing for a parameter you need to 'excite' the DUT and measure its response. At the minimum, this would involve two pins. If you're using Kelvin contacts, this would require 4 contacts (2 per pin). One of the fingers is for forcing the excitation (say, current) through the test pin and the other is for measuring the response (voltage) directly from that pin. Of course, the return pin would likewise have corresponding 'force' and 'sense' pins. The reason why you want a separate set of fingers for measurement is to avoid the IR drops through the path used for excitation, which can result in large error measurements if the forced current is large. The fingers used for measurement can measure the voltage with very minimal current, so the IR drops through this path is negligible. Yes, it is bad if one of the fingers (whether it's the 'force' or 'sense' pin) breaks off completely, because the force/sense system will fail. You have just inspired us to write an article on various contacting methods, so watch out for this. Anyway, thanks and keep on posting! EE Last edited by EE on Mon Aug 11, 2026 10:00 am; edited 1 time in total |
|
  |
Joined: 20 Jun 2026
Posts: 17
| Posted: Mon Aug 11, 2026 9:58 am Post subject: |
|
| EE, there are instances when you don't need kelvin connection. So, you don't need 4 contacts always, right?
Test Engg Engg 99 |
|
| |
Joined: 16 Jun 2026
Posts: 109
Location: Paranaque City, Phils.
| Posted: Fri Aug 15, 2026 1:38 pm Post subject: |
|
| Yes, you don’t need Kelvin connection at all times to test a part. It is only necessary when the amount of current you need to force into a pin is large enough to cause IR drops that will result in measurement errors. An examples of this is when you’re measuring very low resistances, i.e., less than 1 ohm.
Thus, the decision whether to use Kelvin connection or not depends on the product you’re testing and your hardware characteristics. Some companies even try to avoid Kelvin connections when possible because they are more complicated and costlier than a 2-wire measurement connection. EE |
|
| |
Guest
| Posted: Thu Aug 12, 2026 4:46 pm Post subject: |
|
| Hi Mang Kelvin;
To add up on what EE and testeng99 answered, mostly we are using kelvin contacts to accuarately measure low current dc test and on soft dock systems to compensate the errors (IR drop) made by wires and board traces. Yes, it is using 2 contacts on a single pin, one is forcing while the other is sensing the forced voltage. Example we are expecting a 0.25 A (example lang) current output. To do this we need to force a certain voltage say 5 volt but due to drops on the wires or added resistance, forced voltage at the pins is not actually 5 volt but less. If less voltage is used then your current reading will not be accurate. The sense pin of kelvin contact will tell the tester that hey force more voltage at the source so that when it reached the DUT it will exactly be 5V. |
|
Guest
| Posted: Tue Aug 31, 2026 5:03 pm Post subject: |
|
| Mang Kelvin,
Tutal naman tagalog pangalan mo.... TAGALUGIN ko na rin sagot ko. OK, una... kaya dalawa ung contact mo sa isang pin, dahil ung isa ay FORCE pin at SENSE naman ung huli. Sabi nila dapat apat daw ang KELVIN.... HEHEHEHE! tama sila, kaso mali ang sagot na dapat apata sila. ung dalawa pang contact ay para FORCE and SENSE ng Ground. Kaya na-design ito ay dahil nga sa sinabi ni KIM.... to produce more accurate measurement/forcing. To cut the answer short.... 4 element ang KELVIN: 1. HIGH FORCE 2. HIGH SENCE 3. LOW FORCE 4. LOW SENCE Sana makatulong.... Flipflop |
|