Hi all!
I've been wanting to do a resistive vhs ribbon sensor, but either my vhs cassettes have really really high resistance (i don't get any value from my multimeter even with 1cm between probes) or they have a high amount of resistance (around 2M Ohms per cm). Anyone knows which VHS tape have lower resistance?
im following this tutorial: http://memoir.okno.be/phys_comp_tutorial/ribbon4/ribbon4.htm
(for some reason i can only access the website though my phone)
Thank you all.
TiagoPT:
Hi all!I've been wanting to do a resistive vhs ribbon sensor, but either my vhs cassettes have really really high resistance (i don't get any value from my multimeter even with 1cm between probes) or they have a high amount of resistance (around 2M Ohms per cm). Anyone knows which VHS tape have lower resistance?
im following this tutorial: http://memoir.okno.be/phys_comp_tutorial/ribbon4/ribbon4.htm
(for some reason i can only access the website though my phone)
Thank you all.
Please point out for me where that link says to use VHF tapes for the sensor.
Paul
Paul_KD7HB:
Please point out for me where that link says to use VHF tapes for the sensor.Paul
The following text taken directly from the link :
Resistive (8mm video) tape: Not all videotape has resistive properties, and not both sides are resistive. Test it with a multimeter. My tape measures about 15 kiloOhm/square (so a strip of 80mm long measures 150kOhm between the ends). All kind of tapes stand a chance to be resistive. But audiocassette tape is a bit small. VHS, 8mm, or audio reel-to-reel tape are better candidates.
TiagoPT:
Hi all!I've been wanting to do a resistive vhs ribbon sensor, but either my vhs cassettes have really really high resistance (i don't get any value from my multimeter even with 1cm between probes) or they have a high amount of resistance (around 2M Ohms per cm). Anyone knows which VHS tape have lower resistance?
im following this tutorial: http://memoir.okno.be/phys_comp_tutorial/ribbon4/ribbon4.htm
(for some reason i can only access the website though my phone)
Thank you all.
Area resistance is measured in ohms per square (or just ohms), not ohms per cm. Since VHS tape has
no specification for areal resistivity I doubt you'll see much consistency between tapes of similar
type as the current has to flow through both magnetic particles and binder, though I'd suspect more
expensive brands use more magnetic particles and thus more particles touch and the resistivity should
be lower. The main magnetic materials used were magnetite (ferric) and chrome-dioxide, its worth
checking if CrO2 conducts electricity at all.
Paul_KD7HB:
Please point out for me where that link says to use VHF tapes for the sensor.Paul
"Resistive (8mm video) tape: Not all videotape has resistive properties, and not both sides are resistive. Test it with a multimeter. My tape measures about 15 kiloOhm/square (so a strip of 80mm long measures 150kOhm between the ends). All kind of tapes stand a chance to be resistive. But audiocassette tape is a bit small. VHS, 8mm, or audio reel-to-reel tape are better candidates."
TiagoPT:
I've been wanting to do a resistive vhs ribbon sensor, but either my vhs cassettes have really really high resistance (i don't get any value from my multimeter even with 1cm between probes) or they have a high amount of resistance (around 2M Ohms per cm). Anyone knows which VHS tape have lower resistance?
I don't have an answer TiagoPT, but I think the experiment is pretty cool and I hope you'll keep us posted on what your learn.
I tried checking resistance between two points on an old floppy disk -- open circuit there as well. I suspect that most VHS tape, like my floppy disk, is coated with a protective layer of mylar or something, since the read/write heads are magnetic and don't need actual contact with the recording medium.
If the tape is shinny on both sides, you probably have a coated tape. You need one (I'm guessing here) that feels a little rough on the conductive side.
PS: Check out something called "teledeltos paper" It's paper that's coated with a resistive carbon film on one side that would be ideal for your experiments. And along those lines, I seem to remember long ago using a high-carbon pencil to make my own resistive paper strips. A charcoal artist's pencil might be worth a try.
I have a piece of VHS tape and measured 400K Ohms with the probes at a distance of ~ 1cm. I used a Fluke ohmmeter (9V).
I mention the ohmmeter because there may be a voltage aspect of the tape conductivity. You may need to exceed some voltage to get current to flow.
The recording surface of this tape was matte in finish. Have you checked both sides of your tape? Actually I have never seen a magnetic tape that was shiny on both sides.
JohnRob:
I have a piece of VHS tape and measured 400K Ohms with the probes at a distance of ~ 1cm. I used a Fluke ohmmeter (9V).I mention the ohmmeter because there may be a voltage aspect of the tape conductivity. You may need to exceed some voltage to get current to flow.
I guess its possible that magnetic coatings act as a VDR, but then its a poor choice for the application really,
too many variables.
Another thing I've remembered is that often magnetic tapes have a surface coating to reduce wear
of the magnetic layer, this is likely not to conduct if present...
I guess its possible that magnetic coatings act as a VDR, but then its a poor choice for the application really,
too many variables.
I only thought of the voltage aspect from working with ESD dissipating materials. Many materials will not conduct with simple (low voltage) ohmmeter but bring the voltage up to 20+ and the conduction becomes much greater. I figured the magnetic particles might act the same way.
I agree the results are likely unpredictable and unstable..... but maybe good enough.