Hey everyone,
I built this o'scope calibration unit I thought everyone would like to see, in case any of you would like to build one as well. First of all, it uses the LTC6655 voltage reference IC and will only have 775nV of noise max, and with an initial accuracy of ±0.025% max. See the datasheet for the circuit schematic (Pg. 1):
http://cds.linear.com/docs/Datasheet/6655f.pdf
It is possible to reduce the noise level to 160nV max, but to do that, more circuitry is required. If your interested in that noise level, see this document:
http://cds.linear.com/docs/Application Note/an124f.pdf
As you may have noticed, I've used a BNC connector for the output of my unit. This will feed directly into your o'scope if you add a female to female connector to make the connection. I also have a DC connector that you can see as the yellow rectangle in the attached pictures. The IC has a range of 3<Vin<13.2V, but I have around 5V going powering the unit from a cell phone wall-adapter. I didn't bother to fasten the PCB to the enclosure since it is so lightweight and because the wires hold it in place. Probably the most difficult portion of building this project was soldering to the IC. The IC is in a SMT MSOP package; and it's hard to get a stubby iron tip in there without shorting those miniscule pins! In fact, I accidentally broke off a pin from my first IC I used.
Enjoy!
Austin
I built this o'scope calibration unit I thought everyone would like to see, in case any of you would like to build one as well. First of all, it uses the LTC6655 voltage reference IC and will only have 775nV of noise max, and with an initial accuracy of ±0.025% max. See the datasheet for the circuit schematic (Pg. 1):
http://cds.linear.com/docs/Datasheet/6655f.pdf
It is possible to reduce the noise level to 160nV max, but to do that, more circuitry is required. If your interested in that noise level, see this document:
http://cds.linear.com/docs/Application Note/an124f.pdf
As you may have noticed, I've used a BNC connector for the output of my unit. This will feed directly into your o'scope if you add a female to female connector to make the connection. I also have a DC connector that you can see as the yellow rectangle in the attached pictures. The IC has a range of 3<Vin<13.2V, but I have around 5V going powering the unit from a cell phone wall-adapter. I didn't bother to fasten the PCB to the enclosure since it is so lightweight and because the wires hold it in place. Probably the most difficult portion of building this project was soldering to the IC. The IC is in a SMT MSOP package; and it's hard to get a stubby iron tip in there without shorting those miniscule pins! In fact, I accidentally broke off a pin from my first IC I used.
Enjoy!
Austin
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