Ceramic Cap: Axial vs Disc??

[Rileyesi]

I have an ancient design that uses 0.01 uF ceramic disc capacitors. I am
considering changing that to an axial ceramic cap. The axial is cheaper and
has tighter tolerance and a wider operating temperature.

Sounds too good to be true! What am I missing??

The application is in an anemometer (i.e. wind speed sensor) that is a
permament magnet DC generator, so there are two wires coming out of the device.
The caps are located between each lead and the metal housing of the sensor.

Any thoughts?

Thanks.

 

[Spehro Pefhany]

On 18 May 2004 18:01:19 GMT, the renowned rileyesi@aol.com.gov
(Rileyesi) wrote:

I have an ancient design that uses 0.01 uF ceramic disc capacitors. I am
considering changing that to an axial ceramic cap. The axial is cheaper and
has tighter tolerance and a wider operating temperature.

Sounds too good to be true! What am I missing??

The application is in an anemometer (i.e. wind speed sensor) that is a
permament magnet DC generator, so there are two wires coming out of the device.
The caps are located between each lead and the metal housing of the sensor.

Any thoughts?

What's the dielectric? You might want to avoid using some Class 2
dielectrics if the product sees extreme temperature because they lose
most of their capacitance under those conditions.

Maybe consider lead-formed monolithic ceramic caps.. I don't think
axial ceramics are all that popular these days.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[John Popelish]

Rileyesi wrote:

I have an ancient design that uses 0.01 uF ceramic disc capacitors. I am
considering changing that to an axial ceramic cap. The axial is cheaper and
has tighter tolerance and a wider operating temperature.

Sounds too good to be true! What am I missing??

The application is in an anemometer (i.e. wind speed sensor) that is a
permament magnet DC generator, so there are two wires coming out of the device.
The caps are located between each lead and the metal housing of the sensor.

Any thoughts?

Thanks.

Just make sure your caps are X5R or X7R type and you should do fine.
Those Y5V and Z5U types vary a lot with voltage and temperture.

--
John Popelish

 

[legg]

On 18 May 2004 18:01:19 GMT, rileyesi@aol.com.gov (Rileyesi) wrote:

I have an ancient design that uses 0.01 uF ceramic disc capacitors. I am
considering changing that to an axial ceramic cap. The axial is cheaper and
has tighter tolerance and a wider operating temperature.

Sounds too good to be true! What am I missing??

The application is in an anemometer (i.e. wind speed sensor) that is a
permament magnet DC generator, so there are two wires coming out of the device.
The caps are located between each lead and the metal housing of the sensor.

It's possible that the location of these parts is important. You
should take into account their re-positioning; lead lengths, integrity
of the frame contact; when turning them into auto-insertable parts.

You did not indicate the voltage rating. Things sticking up in the
atmosphere generally have to anticipate high levels of ESD and surge,
without failure. This has a price.

Why are you not redesigning for smd, if you're serious about the
product? Axial components are increasingly difficult to source, and
are losing cost-competitiveness.

RL