11. Electrical Isolation#
The Joulescope is electrically isolated between the USB interface and the sensor terminals. Joulescope is rated to ±48V between USB ground and any of sensor terminals: Current +, Current -, Voltage +, and Voltage -. The ±48V is limited by the aluminum enclosure and the fit within low-voltage safety requirements.
The individual component ratings far exceed this specification. The components are:
Part # |
Mfgr |
Description |
Isolation working |
Isolation 60s |
Isolation 1s |
|---|---|---|---|---|---|
750316018 |
Wurth |
Transformer |
400 VRMS |
2500 VAC |
3125 VAC |
ISO7762 |
TI |
Digital isolator |
445 VRMS |
4500 VRMS |
|
TLP2361(TPL,E |
Toshiba |
Opto isolator |
500 VRMS |
3750 VRMS |
The printed circuit board (PCB) clearance between the isolated sensor side and the USB host side is 1 mm. The use of an aluminum enclosure effectively limits the isolation voltage and requires that USB chassis ground surrounds the sensor edges.
While all the sensor terminals are isolated from USB ground, they are not isolated from each other. The sensor is referenced to Current +, and the other sensor terminals must remain within ±15V from Current +.