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Test leads comparison with new Invention
Comparison between test leads clips: parrot , alligator, one hook, two hooks, gripper, grabber, pincer reveal advantages of the Parrot Clip at the majority of the parameters which are relevant.
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There are test and measurement activities with multimeters, oscilloscopes, spectrum analyzers etc., which need probes, test leads to perform two kinds of removable contacts and connections:
1) Hands-on, point contact, when the probe is hand-held and pointed to the test probe performing a direct point contact
2) Hands-free, clip–on, when the clip is connected to the test point and the hands are taken away from the clip performing a connecting contact.
There are some well known devices performing this function:
a ) Alligator( crocodile) clips, - characterized by 2 jaws having a rotation movement and a spiral spring .
b) One hook clip – known under different names: gripper, grabber, pincer characterized by one metal hooked rod , directly connected to the wire lead .
The metal rode has a hook on one end and an insulated, spring loaded, push-button on the other. The button is pressed with the finger and then released to provide a grip between the metal hook and the plastic tube tip of the clip.
c) Two hooks clip – having different names gripper, grabber, pincer
characterized by 2 metal rods with the 2 hooks at one end and an insulated, spring loaded, push-button on the other . The rods are connected to the wire lead by the mean of a metal sleeve .The rods are sliding along the sleeve which is included in the body of the probe.
The grip is made by the 2 hooks which are caching the device between them.
d) A new device, the Parrot clip, has as a novelty a metal tube tip. The metal tube is oval and has a sharp tip on one side. On the other end of the tube is soldered the wire lead ( Fig ) .
A hooked rode is moving inside the metal tube. . The metal rode has a hook on one end and an insulated, spring loaded, push-button on the other. The button is pressed with the finger and then released to provide a very good grip between the metal hook of the rode and the metal tube tip.
The metal oval tip, the hook-ended rod and the spring are housed in a plastic support, which is included in a plastic body which assures convenient handling and high insulation.
A plastic support is pressed inside the body for assembling. With a screwdriver it can be easy taken out from the body for disassembling when needed. The body has barriers for the fingers to meet IEC insulation Cat II, III requirements.
The end of the metal tube tip is directly connected the lead, so both the direct contact resistance and the connection resistance are very low.
The connection is reliable and accurate as is made between the metal tip and the steel gripper hook under the pressure of the spring when the finger is released from the button.
Depending of the Hooks width and Tips Width the Parrot Clip can be used for gripping different devices and sizes at different currents.
The following comparation of test probes and clips is made according to the parameters which are relevant for test probes.
Parameters 1,2, 3 refer to the hands-on, direct point contact and parameters 4,5,6 are referring to the hands-free, connection .
Parrot Clip:
1) Direct point Contact Resistance- low, due to the sharp tip soldered directly to the lead.
R < 5 mohm
2) Direct point Contact Accessibility in narrow places - good, due to the thin tip
3) Insulation Signal- Operator - very good, allows good insulation and also easy assembling and disassembling.
4) Connection Resistance - very low , due to the double metal connection and direct soldering of the tip to the lead, R < 5 mohm
5) Connection Accessibility in narrow places - good, but has to be adapted for specific measurement
6) Connection Reliability - very good, electrical and mechanical, even at high temperatures.
Alligator Clip:
1) Direct point Contact Resistance- bad , no sharp tip available
2) Direct point Contact Accessibility in narrow places - bad , needs lot of space
3) Insulation Signal-Operator - bad, high insulation difficult to achieve
4) Connection Resistance –good, due to the double metal connection
5) Connection Accessibility in narrow places –bad, due to the need of lot of space
6) Connection Reliability -medium, depending of the shape of the test point or device , can be affected by movement of lead.
One Hook Clip:
1) Direct point Contact Resistance- poor, made with a round part of a hook
2) Direct point Contact Accessibility in narrow places - poor and uneasy, needs continuous finger pressing and is made with a round part of a hook
3) Insulation Signal- Operator - medium, high insulation difficult to achieve
4) Connection Resistance - medium, connection made between one metal hook and one plastic tip.
5) Connection Accessibility in narrow places - medium, plastic tip doesn't allow much miniaturization
6) Connection Reliability - bad, mechanical unreliable and affected by plastic melding at high temperatures
Common Test Lead
1) Direct point Contact Resistance- very good
2) Direct point Contact Accessibility in narrow places - very good
3) Insulation Signal- Operator - very good
4) Connection Resistance - missing
5) Connection Accessibility in narrow places - missing
6) Connection Reliability - missing
Conclusions
The miniaturization of electronic equipments has limited applications where griping clips are needed for prototypes, test and repair, But still there are gripping clips demanded by professional or hobby users. They are used either for test and measurement activities or for other non-permanent connecting.
There are applications where one particular probe is most efficient.
For large devices the Alligators clip is a good solution. But in most applications the Parrot clip provides more advantages to users, like high insulation, better accessibility in narrow places, and better direct contact due to the sharp tip. The Two Hooks clip has still practical advantages for connections to very small pins of integrated circuits. Connections on SMD can be made either with Parrot Clips , either with 2 hooks clips.
References:
USA patent 5,457,392
European patent 0563234.
Parrot Clip – is a trade mark of Parrot Invent srl, , http://www.parrot-invent.com
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