50Mhz Square wave generation.

[Hoobbyy_Engineer]

Hi,
I am trying to generate a square wave of frequency 50Mhz.What is the best way(also cheap way) to get a 50Mhz decent square wave which does not vary much with temperature?

Thanks

 

[Arouse1973]

He you go. http://uk.farnell.com/b-k-precision...Ut_DZkhoCHH7w_wcB&CAWELAID=120173390002087231

Thanks
Adam

 

[Harald Kapp]

He you go. http://uk.farnell.com/b-k-precision...Ut_DZkhoCHH7w_wcB&CAWELAID=120173390002087231

A bit expensive for a "best way".

A 50 MHz oscillator circuit is much cheaper. The MEMS type oscillators can be had rater temperature stable, too,

 

[Externet]

Should be a couple of $ ----> http://img.alicdn.com/imgextra/i1/44075510/TB2qdSUaNfxQeBjSspjXXX4opXa_!!44075510.jpg

 

[AnalogKid]

$0.90, single piece:
https://www.digikey.com/product-detail/en/sitime/SIT2001BI-S2-33E-50.000000G/1473-1346-1-ND/5824455

ak

 

[Hoobbyy_Engineer]

Hi,
Thanks for the replies.But I am not looking for any IC that can generate a square wave. I am in need of an analog circuit to get 50Mhz.

Regards

 

[davenn]

Hi,
Thanks for the replies.But I am not looking for any IC that can generate a square wave.

Regards

I hope you are not going to put an antenna on that, you will upset a lot of people !

I am in need of an analog circuit to get 50Mhz.

why ??
Harald gave you a whole page of excellent choices what is wrong with them ... specifically

you understand that a square wave that you asked for is basically a digital signal, aye ?

You had better explain clearly what you are trying to achieve

 

[Hoobbyy_Engineer]

I hope you are not going to put an antenna on that, you will upset a lot of people !



why ??
Harald gave you a whole page of excellent choices what is wrong with them ... specifically

you understand that a square wave that you asked for is basically a digital signal, aye ?

You had better explain clearly what you are trying to achieve

I am trying to make a capacitive soil moisture sensor.
The concept is to charge the capacitor( sensor) with a square wave and measure the peak voltage stored in it. So as the moisture content of soil changes , the capacitance of sensor will change,resulting in change in peak voltage.So does it really require an ic?(I want to keep costs as low as possible)

Regards,
Nilesh

 

[davenn]

So does it really require an ic?(I want to keep costs as low as possible)

it's the best way to satisfy your bracketed comment

 

[AnalogKid]

Does it really require 50 MHz? Can you post a justification for this requirement?

Please read post #1.

If this is for a product, you just volunteered for a ton of certification and compliance testing.

ak

 

[Hoobbyy_Engineer]

Does it really require 50 MHz? Can you post a justification for this requirement?

ak

Hi,
Higher the frequency, more it is insensitive towards minerals and salts.

If this is for a product, you just volunteered for a ton of certification and compliance testing.

Nope, it is for personal use.I am going to use it in my grapeyard.

 

[davenn]

Nope, it is for personal use.I am going to use it in my grapeyard.

beware that you don't cause your signal to go too far ..... 50MHz is a commercial and also an amateur radio frequency in most countries
as I said earlier, you could upset a lot of people .... 50MHz will radiate 1000's of km's when the propagation is right

what power level were you looking at using ?

 

[(*steve*)]

A colleague of mine has built a soul moisture probe based on a capacitive sensor.

The major problem is protecting your sensor from the environment. If you don't, your readings will drift over time.

 

[duke37]

To measure capacitance you do not need a square wave, a sine wave would do.
To get a square wave you need lots of odd harmonics so if only going to the 5th harmonic, the circuit must be able to handle 250MHz without phase distortion.

 

[Hoobbyy_Engineer]

beware that you don't cause your signal to go too far ..... 50MHz is a commercial and also an amateur radio frequency in most countries
as I said earlier, you could upset a lot of people .... 50MHz will radiate 1000's of km's when the propagation is right

what power level were you looking at using ?

It will be about 50mW. The whole sensor will be underground so I don't think it will cause any problems.

 

[Hoobbyy_Engineer]

The major problem is protecting your sensor from the environment. If you don't, your readings will drift over time.

Yep, I am using a layer of epoxy to isolate it from corrosive environment.

To measure capacitance you do not need a square wave, a sine wave would do.

That is interesting. Can you explain how it is done.

Thanks

 

[Harald Kapp]

Yep, I am using a layer of epoxy to isolate it from corrosive environment.

How is the sensor to measure humidity if it is isolated by epoxy from the environment?

That is interesting. Can you explain how it is done.

You know Google? -> https://meettechniek.info/passive/capacitance.html

 

[AnalogKid]

My guess is that he is by measuring the capacitor voltage after a fixed charge time (shunt mode). With a sine wave you could measure the capacitor impedance (series mode) in a half-bridge. Either way, changing soil moisture content might change the dielectric properties enough to affect the capacitance value, even if isolated by epoxy, but the change will be very small.

ak

 

[Hoobbyy_Engineer]

How is the sensor to measure humidity if it is isolated by epoxy from the environment?

If water comes in contact with the uncoated capacitor it will not simply remain a capacitor! Here we are measuring the parasitic capacitance, similar to capacitive touch sensors.

Here is a circuit diagram that I found on https://wemakethings.net/2012/09/26/capacitance_measurement/

In this case the clock is 8 Mhz. I want to replace it with 50Mhz.

 

[Arouse1973]

A bit expensive for a "best way".

A 50 MHz oscillator circuit is much cheaper. The MEMS type oscillators can be had rater temperature stable, too,