Anyone have any experience with the ETA - 1110-F112-P1M1-5A – circuit breaker/switch? Jonker used these on the early JS-1. See: http://www.newark.com/eta/1110-f112-...-5a/dp/98K5389

Tuesday, October 22, 2013 4:00:27 PM UTC-4, JohnDeRosa wrote:
On Sunday, October 20, 2013 12:31:32 PM UTC-5, Darryl Ramm wrote:



Capitalized ZERO, like you really mean absolutely zero, nothing, zilch, nada?

Ah in a word. No. A fuse will *not* have ZERO voltage drop. A typical fuse

for a few amp application might have a voltage drop of ~100mV to ~200mV drop

at the fuse rated current, and that depending on the fuse type and ratings).



Darryl - Mea Culpa. Yep, you got me on that one. Maybe I will do better this time.



Both fuses and breakers have an internal resistance which translates into a voltage drop (which depends on how much current you are drawing). Lets talk about a 1A load for nice round numbers (YMMV).



Littlefuse 3AG fuse specifications (common glass tube);



Rating Internal Voltage Drop Voltage Drop

Resistance at rated Current at 1A

==== ========== ================ ============

1A 0.19 0.19 0.19

2A 0.07 0.14 0.07

3A 0.04 0.13 0.04

4A 0.03 0.12 0.03

5A 0.02 0.11 0.02



Klixon CT series breaker specifications;



Rating Internal Volts Drop Voltage drop

Resistance at rating current at 1A

==== ========== ================ ============

1A 1.10 1.10 1.10

2A 0.35 0.70 0.35

3A 0.13 0.40 0.13

4A 0.09 0.37 0.09

5A 0.07 0.35 0.07



Take aways;



- Fuses have significantly lower voltage drops than breakers by an average of 4x ... but it AIN'T ZERO!

- The higher the current circuit protection device rating, the less voltage drop.

- Covering your panel with low rated fuses or breakers for each and every instrument isn't a good idea.

- Circuit protection devices in series with another device compounds the problem. For example a master fuse sourcing individual device fuses. Each layer drops more voltage.

- As had been said over and over again in this and other RAS threads, and bears repeating, a single large value fuse at the battery is your single best overall safety bet.

- One last thing - Per most manufacturers breakers should not be used as on/off switches. The only one I have found that can be used as an on/off switch is the Tyco W30 and W31 series.



- John