- Joined
- Jun 18, 2024
- Messages
- 23
What do people recommend for the bench? One top contender I've gathered for a combined iso-variac is the Sencore PR57 (one for $400 and one for $600 on eBay, though the $600 one is modified, with the front plug disconnected and a plug added through the back). Others I've found are the Global Specialties 1504 ($400 on eBay) and the B&K Precision 1655/1653 ($200-300 on eBay).
Do people recommend any of these, or would it be best to get a separate ISO and Variac?
I also had a newbie tech question. Is the PR57 fully or truly isolated? I was watching a video on the PR57 and a commenter noted that the schematics for the PR57 show that the earth-ground for the PR57's power plug is shown to chassis ground (first pic) and the earth-ground for the PR57's isolated output is also shown to chassis ground (second pic). The commenter says: "They are effectively connected. On your household power socket the earth-ground and AC-neutral (long slot) are tied together at the breaker box. Basically what ever you plug into the ISOLATED OUTPUT of the PR57 will share the same chassi ground (potential) as anything else that's plugged into your household socket. The PR57 will not protect you or your scope from a Hot chassis or high side of a SMPS."
Another commenter followed up on what this person said: "[Above commenter] is correct: The issue is that the ground is not isolated (check for continuity between the input ground plug and the isolated output socket and you will see). Most American household electrical panels have the ground and neutral bonded, therefore the Sencore's "isolated" output ground pin is effectively connected to the input neutral as well. The simple way to solve this is to float the ground - do so at your own risk...."
So this leaves me a bit confused as to how this unit is an isolation transformer, if the above is correct. It also leaves me unsure as to what I should get for an ISO. Basically I want an ISO that I can use to help prevent me from accidentally blowing up my scope.
Thanks everyone for your help.
Do people recommend any of these, or would it be best to get a separate ISO and Variac?
I also had a newbie tech question. Is the PR57 fully or truly isolated? I was watching a video on the PR57 and a commenter noted that the schematics for the PR57 show that the earth-ground for the PR57's power plug is shown to chassis ground (first pic) and the earth-ground for the PR57's isolated output is also shown to chassis ground (second pic). The commenter says: "They are effectively connected. On your household power socket the earth-ground and AC-neutral (long slot) are tied together at the breaker box. Basically what ever you plug into the ISOLATED OUTPUT of the PR57 will share the same chassi ground (potential) as anything else that's plugged into your household socket. The PR57 will not protect you or your scope from a Hot chassis or high side of a SMPS."
Another commenter followed up on what this person said: "[Above commenter] is correct: The issue is that the ground is not isolated (check for continuity between the input ground plug and the isolated output socket and you will see). Most American household electrical panels have the ground and neutral bonded, therefore the Sencore's "isolated" output ground pin is effectively connected to the input neutral as well. The simple way to solve this is to float the ground - do so at your own risk...."
![1722268509679.png](/data/attachments/79/79420-6247b457fb67f31bfce261e9801e16c9.jpg)
![1722268838070.png](/data/attachments/79/79421-395f46be3d464728b17233f181af225f.jpg)
So this leaves me a bit confused as to how this unit is an isolation transformer, if the above is correct. It also leaves me unsure as to what I should get for an ISO. Basically I want an ISO that I can use to help prevent me from accidentally blowing up my scope.
Thanks everyone for your help.