I'm sorry about all the delays, reference module for US Cal Club is shipped today.
Initial calibration data and measured stats:
![](https://xdevs.com/doc/xDevs.com/FX/usac/final_spec_1.png)
My lab will get new SI Volt (doing JJA cal for my refs soon), so I will be able to confirm/deny the absolute uncertainty of my setup. Two 3458A and K2002 were used to perform all measurements.
![](https://xdevs.com/doc/xDevs.com/FX/usac/usac_ctop_1.jpg)
![](https://xdevs.com/doc/xDevs.com/FX/usac/usac_cable_1.jpg)
Output provided by two Pomona 3770 low thermal EMF posts. Input power and auxilary circuitry using circular shielded connector (fanout cable included in package).
Power requirements : +11 to +15VDC, -2 to -15VDC, current limited at least 80mA. Power input is protected by 125mA fuse and TVS.
Optional PCB temperature sensor : MAX6610 (U4 on PCB), with isolated power +5V.
Optional ROM data storage: I2C EEPROM with isolated +3.3V power (ground shared with temp sensor).
Calibration data provided for temperature range +20 °C to +50 °C
![](https://xdevs.com/doc/xDevs.com/FX/usac/usac_face_1.jpg)
Chip is LTZ1000A, setpoint 12.5/1K TCC VHP200 divider. Onboard regulator for LTZ1000A section is LT3042. Schematics is otherwise same as Linear's datasheet.
![](https://xdevs.com/doc/xDevs.com/FX/usac/usac_rnet_1.jpg)
Output amplifier is Analog ADA4522-2 chopper, together with bipolar transistor driver. Reference can survive short at the output for indefinite time.
FX module output driver can sink or source up to 20mA, but here module cannot maintain output accuracy because kelvin sense lines are not routed to the binding posts.
Inline fuses are hidden in yellow tube. Suggest not to break them
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
Just realized, somebody melted few film cap casing
![](https://xdevs.com/doc/xDevs.com/FX/usac/usac_wiring_1.jpg)
![](https://xdevs.com/doc/xDevs.com/FX/usac/usac_ldo_1.jpg)
Looking forward to see results on this by US members. I would recommend not to open the box to avoid magic ppms leaking out
![Popcorn :popcorn:](https://www.eevblog.com/forum/Smileys/default/EatingPopcorn.jpg.pagespeed.ce.yJ6TmC5fSa.jpg)