BG7TBL FA-5-6GP Frequency Counter inside and some tests

[KedasProbe]

Hi,

Some PCB pictures for those that are interested,
PCB board is year 10/2021 and firmware 6/2024
Gate-time maximum is 20sec, above it it waits that long but gives wrong data.
Serial commands in the zip file.


I wrote a program for it since there is no screen on it, if it's not easy to read it's annoying to me anyway, so I decided I can use the one without screen and write a program for it.
It's based on an existing general serial communication program. https://github.com/mcagriaksoy/Serial-Communication-GUI-Program

(Note: I wanted to add some time graphs but I couldn't get it to work, library compatibility....)


EDIT:
- There is no power switch but the PCB board does have a connector for it, if you remove the solder join on the connector pins, at the front left from the led there is some room for a hole.
- I updated excel file so the graphs load faster
 offset is changing with gate-time but also with freq it seems (see offset dip 10Mhz at 1sec and 100Mhz at 0.1sec).
- serial communication is a bit tricky since you have to wait until the measurement is done before it does something and it only remembers the last command given, this can feel like it doesn't work at long gate-times.

[KedasProbe]

Some extra info to reflect on:
Input impedance of CH1 is around 50\$\Omega\$ but for CH2 it's around 32\$\Omega\$

Source code of my program:  https://github.com/Ken26M/FA-5-6GP_MonitorControl
It can store all measurements with a timestamp, the statistics are also added to a csv file when you copy to clipboard.
Even if you use the timelab program to record you can change the settings with this program and then
press disconnect and connect with timelab.

edit:
The program does not use floats (64bit) for the long frequency numbers but decimals.

If you want to use it for an other device like FA-2 or FA-3 you will need to change the parsing code in fa5usbdata.py, function 'add_string' and probably also the line if serial_data[0] == "$" in ui_main.py that decides in which textbox the text line must be displayed.

You may need to install a driver https://ftdichip.com/Drivers/vcp-drivers/ if you see only a USB device and not a com port.

[GigaJoe]

seem same as fa-2 / 3 ; but no display

btw,  the correction  voltage for VECTRON , from tl431 , it connected to input 12v , over regular  resistor, and very sensitive to input  12v voltage
so ideally need very stable 12v input or redesign correction voltage source; or something ext stable Fref
TL431 itself quite   drifty over time.

[KedasProbe]

I did some measurements and it does not seem to be very power supply sensitive.
I only see about -0.3 PPB/V  around 12V
If you change the power supply voltage with 1 volt you have to give it a minute to settle down again (see step response graph)

I also included the warm up time that is long, about -8mHz/hour or -0.8PPB/hour, 1 hour after power on.
You should at least wait 2 minutes before using it but that is normal for an OCXO.

All measurements were done with a gate time of 2sec and a GPSDO 10MHz source signal to measure.

P.S. I didn't add a power switch on the device to avoid adding holes, I added an external switch on the 12V line.