I have an SRM 100/3a kit I found on EBay. It is designed for measuring surface resistivity in static controlled environments. Very expensive to buy new, perhaps worth keeping an eye open for.
Anyway it comes with a square device containing two parallel contacts that form two sides of a square. The resistance of a surface between these two electrodes comes out in 'Ohms per square' and is the relevant figure for diaphragms.
If I recall my school physics then the resistance between any two points on an infinite plane of constant resistivity is the same, and is the 'Ohms per square' value. In practice if you're measuring between two points with a meter as long as the two points are closer together than the smaller dimension of your diaphragm the measurement should be the same wherever you take it.
Anyway I can say that the coating on a Quad ESL63 is 10^8 Ohms. Which may be useful to someone...
More interestingly it is grey and appears to be painted onto a white underlayer that shows through in a sort of mottled effect. Does anybody know what they used, and why?
Paul
Anyway it comes with a square device containing two parallel contacts that form two sides of a square. The resistance of a surface between these two electrodes comes out in 'Ohms per square' and is the relevant figure for diaphragms.
If I recall my school physics then the resistance between any two points on an infinite plane of constant resistivity is the same, and is the 'Ohms per square' value. In practice if you're measuring between two points with a meter as long as the two points are closer together than the smaller dimension of your diaphragm the measurement should be the same wherever you take it.
Anyway I can say that the coating on a Quad ESL63 is 10^8 Ohms. Which may be useful to someone...
More interestingly it is grey and appears to be painted onto a white underlayer that shows through in a sort of mottled effect. Does anybody know what they used, and why?
Paul
I have always used a mixture of VELPON school glue. It is a transparant hobbyglue. I dilute it with water, add some drops of blue airbrushpaint and apply it with an airbrushpistol.
I measure with a megger (dont know the word in english) from work.
It is a measuring instrument used to control the dielectric strengt of cables and other electrical circuits.
The one I use is a professional one used in High Voltage cabines.
You can megger with tensiones between 500V and 7500V and measure up very high resistance.
Geert
I measure with a megger (dont know the word in english) from work.
It is a measuring instrument used to control the dielectric strengt of cables and other electrical circuits.
The one I use is a professional one used in High Voltage cabines.
You can megger with tensiones between 500V and 7500V and measure up very high resistance.
Geert
Paul Ranson said:
Hi Paul,
It is already some years ago I coated and measured.
I am currently building 4 new ESL's and will apply the same coating very soon and measure it. I'll post the results.
Maybe I can do a test this weekend.
As I remember it was between 1Gigaohm and 3Gigaohm.
greets
geert
I lucked into an HP 4329A at a surplus sale. These are high resistance ohm meters that read from 500K ohm to 2x10^16 ohms! They are ideal for the measurements needed for ESL development and repair. Keep an eye out on eBay or elsewhere. They don't show up often, but they shouldn't be too pricey when they do. (At the same sale, I also bought a sister product, the 4328A, which is just the opposite kind of meter; it measures milliohms, but also useful for audio.)
Attachments
Weldbond is just PVA...
White glue as is used in wood working You should be able to find white glue (pva) just about anywhere in the free world. I would hazard that it is probably the most common adhesive available. School supply office supply and hardware stores all carry it. It is very popular as it is non toxic. Have a look and experiment a little as you can usually purchaes small bottles for very little money.
White glue as is used in wood working You should be able to find white glue (pva) just about anywhere in the free world. I would hazard that it is probably the most common adhesive available. School supply office supply and hardware stores all carry it. It is very popular as it is non toxic. Have a look and experiment a little as you can usually purchaes small bottles for very little money.
If you want to make sure...
and you don't want to rebuild your panels in the event of a failed experiment why not just buy a bottle of Martin's coating? It is the real deal and probably the best solution that you can use. You will have support from one of our own and be supporting him also at the same time. You can also buy some very thin polyester film from him (3 - 4 microns) to build the best ESL's you can.
and you don't want to rebuild your panels in the event of a failed experiment why not just buy a bottle of Martin's coating? It is the real deal and probably the best solution that you can use. You will have support from one of our own and be supporting him also at the same time. You can also buy some very thin polyester film from him (3 - 4 microns) to build the best ESL's you can.
I have a Radiometer IM6 Megohmmeter. It can measure up to 10^12 Megohms and the measuring voltage is adjustable from 1 to 999 Volts. It can also measure leakage currents in the order of pikoAmperes. I use it for conditioning electrolytic capacitors in tube stuff, but I think it comes useful at electrostatics, as well.Brian Beck said:
I'm afraid I'm not following this. Are you talking about connecting the high voltage bias supply in series with the diaphragm and multimeter and energizing the power supply? And how is the calculation done?
Hi,
To estimate the coating´s resistance (named R1) You need to know the HV-Supply-voltage. You need a measuring electrode (or 2 contacts), a resistor (named R2) of known value in the range 100kOhm-1Mohm and a multimeter.
You place the measuring electrode´s contacts on the Diaphragm, say one at the left, the other at the right rim. One contact is connected to the HV-supply, the other to the resistor. The resistor´s second leg is connected to gnd (which is where it connects to the HV-Supply as well and closes the cuttent-loop). Connect the multimeter across the resistor (Range: DC-voltage of a few Vs) and measure the voltage over it.
Declarations:
R1: unknown resistance of diaphragm coating R2: known resistance of measuring resistor
Us = DC-Voltage of HV-Supply (several kV)
I = current through R1 and R2 (µA or less)
U1, U2 = voltages over the associated resistances R1, R2.
Now you can calcualte two ways.
1) calculation by relationship of values.
The resistance and the coating´s resistance form a voltage divider. The voltages over these resistors behave like the resistance values.
U1/R1=U2/R2 --> R1=R2*U1/U2 with U1 beeing exactly Us-U2 (in a first approximation U2 is negligible compared to Us and U1 becomes app. Us)
which leads to R1~=R2*Us/U2
but exactly: R1= R2*(Us-U2)/U2 --> R1=R2*{(Us/U2)-1}
Example:
Us=3kV, R2=100kOhm, U2=100mV
R1~3exp9 Ohm=3GOhm
exact: R1=2.9999exp9Ohm=2.9999GOhm
2) calculation by current:
i= U2/R2 (very small value)
R1= U1/i with U1=Us-U2
--> R1=(Us-U2)/i
Example:
i=100mV/100kOhm=10exp-6A=1µA
R1=(3000V-0.1V)/100µA --> R1=2.9999GOhm
Remark: In praxis the values depend alot on electrode design/layout and the circumstances (e.g influence of the internal resistance of the multimeter is not included in the calculation). It just gives an idea or an approximation about the range of the coating´s resistance value. It´s no method to determine precise and reliable values.
jauu
Calvin
To estimate the coating´s resistance (named R1) You need to know the HV-Supply-voltage. You need a measuring electrode (or 2 contacts), a resistor (named R2) of known value in the range 100kOhm-1Mohm and a multimeter.
You place the measuring electrode´s contacts on the Diaphragm, say one at the left, the other at the right rim. One contact is connected to the HV-supply, the other to the resistor. The resistor´s second leg is connected to gnd (which is where it connects to the HV-Supply as well and closes the cuttent-loop). Connect the multimeter across the resistor (Range: DC-voltage of a few Vs) and measure the voltage over it.
Declarations:
R1: unknown resistance of diaphragm coating R2: known resistance of measuring resistor
Us = DC-Voltage of HV-Supply (several kV)
I = current through R1 and R2 (µA or less)
U1, U2 = voltages over the associated resistances R1, R2.
Now you can calcualte two ways.
1) calculation by relationship of values.
The resistance and the coating´s resistance form a voltage divider. The voltages over these resistors behave like the resistance values.
U1/R1=U2/R2 --> R1=R2*U1/U2 with U1 beeing exactly Us-U2 (in a first approximation U2 is negligible compared to Us and U1 becomes app. Us)
which leads to R1~=R2*Us/U2
but exactly: R1= R2*(Us-U2)/U2 --> R1=R2*{(Us/U2)-1}
Example:
Us=3kV, R2=100kOhm, U2=100mV
R1~3exp9 Ohm=3GOhm
exact: R1=2.9999exp9Ohm=2.9999GOhm
2) calculation by current:
i= U2/R2 (very small value)
R1= U1/i with U1=Us-U2
--> R1=(Us-U2)/i
Example:
i=100mV/100kOhm=10exp-6A=1µA
R1=(3000V-0.1V)/100µA --> R1=2.9999GOhm
Remark: In praxis the values depend alot on electrode design/layout and the circumstances (e.g influence of the internal resistance of the multimeter is not included in the calculation). It just gives an idea or an approximation about the range of the coating´s resistance value. It´s no method to determine precise and reliable values.
jauu
Calvin
Mavric,
The purchased coating solution that I'm donating to your project works superbly, as you heard for yourself. The only problem with it is that I don't know what's in it so I can't share it. If I can use some of the ideas contributed in this thread to devise an easy, inexpensive DIY coating that works well, I will post the recipe here and on my ESL blog page.
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