What is "Zero Voltage" power pack ? - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: December 23, 2011, 09:45:09 am
content: When browsing ebay, found this here ->http://www.ebay.com/itm/Leeds-Northrup-Zero-Voltage-Power-Pack-/310361153254Don't have any plan to acquire it, its just I'm so curious why its called "ZERO VOLTAGE" power pack ?It looks like sort of power supply unit to me, but c'mon, a psu that supplies zero volt ? I'm completely lost.

author: Psi
author_rank: Super Contributor
timestamp: December 23, 2011, 09:48:17 am
content: dunno, need to see inside.From the text its probably some sort of power supply.

author: Simon
author_rank: Unknown
timestamp: December 23, 2011, 09:58:05 am
content: sounds odd to me

author: BravoV
author_rank: Super Contributor
timestamp: December 23, 2011, 10:02:00 am
content: Quote from: Psi on December 23, 2011, 09:48:17 amTo add more confusion, the contradicting message on the "high voltage" warning sign.I'm pretty sure with that LN brand tag, this ain't funny stuff.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 23, 2011, 10:06:28 am
content: Probably referring to zero-voltage switching

author: Simon
author_rank: Unknown
timestamp: December 23, 2011, 10:12:32 am
content: The problem is more the description or lack of than the actual unit in question. it outputs 120VAC and 0.8VDC, does it even have an input ? unless you make assumptions the description could match a perpetual motion machine

author: Bloch
author_rank: Unknown
timestamp: December 23, 2011, 01:11:30 pm
content: http://www.osti.gov/bridge/servlets/purl/5994598-plp3Bc/5994598.pdfQuoteEasy more questions ?

author: Simon
author_rank: Unknown
timestamp: December 23, 2011, 01:16:04 pm
content: so maybe it is actually a low voltage supply for a heater ? like welding

author: caroper
author_rank: Regular Contributor
timestamp: December 23, 2011, 09:44:23 pm
content: WOW, you guys are firing up long forgotten memories here.My Last job in Electronics was with Leeds and Northrup, back in the 80's, but I was working with the "fancy new microprocessor stuff" that had just come out so I had little exposure to the older Analog instruments.That said, the "Zero Voltage" power pack was used in our differential temperature control applications.I only ever interfaced with it on a 4-20mA current loop and never actually saw one in the wild, but I think Simon's call is a good one, it probably controls a furnace based on the comparative readings of several thermocouples.In modern language it would be a high value constant current source.EDIT: In fact I think it was the supply for the 4-20mA current loop, the measuring instrument then adjusted the current and the furnace fired according to the result.My digital stuff was reading the loop to monitor the furnace/thermocouple.It was 30 years ago though so take it as a seed of an idea for research, not as stated fact.

author: Simon
author_rank: Unknown
timestamp: December 23, 2011, 09:48:34 pm
content: ah yes constant current source, indeed if memory serves the ideal current source has 0 voltage (unless required)

author: Zero999
author_rank: Super Contributor
timestamp: December 23, 2011, 10:14:35 pm
content: An idea constant current source has an open circuit voltage of infinity and a short circuit voltage of 0V. The current is the same regardless of the resistance placed across the output terminals.

author: BravoV
author_rank: Super Contributor
timestamp: December 24, 2011, 06:25:04 pm
content: Quote from: caroper on December 23, 2011, 09:44:23 pmThanks a lot, so its just a CC power supply, now that sounds a lot better than the confusing "zero voltage".After reading the document pointed by Bloch, apparently its for metal cooking stuffs, definitely way out of my league.

author: chrome
author_rank: Regular Contributor
timestamp: December 27, 2011, 03:20:38 pm
content: I've found this:"Agilent Zero Volt Electronic Load"

author: firewalker
author_rank: Super Contributor
timestamp: December 27, 2011, 03:56:32 pm
content: If I remember correctly an ideal current source will produce infinite voltage in open circuit and zero voltage when in short circuit.Alexander.Quote from: Simon on December 23, 2011, 09:48:34 pm

author: IanB
author_rank: Super Contributor
timestamp: December 27, 2011, 08:50:17 pm
content: Quote from: BravoV on December 24, 2011, 06:25:04 pmGiven the information above I rather doubt it's a constant current supply. Most likely it is an electronically controlled variable power supply. The 4-20 mA input signal would define a 0-100% power output level and the power supply would set the output power accordingly. The "zero voltage" bit would come from switching the AC cycles at the zero crossing points to avoid noise. Switching the power in whole cycles would cause unacceptable flickering for lighting applications, but with the large thermal inertia of heaters such a method of power control would be fine.That's my guess, anyway.