Powering scope and func gen. - Page 1
Forum section: electronics / beginners

author: tombaxter97
author_rank: Contributor
timestamp: October 25, 2017, 02:35:56 pm
content: Hi all,first time on this forum. Just acquired a HAMEG HM605 and a phillips PM5131, I've got into electronics though making guitar pedals and thought it was about time to get myself a scope and gen. Grabbed them off ebay and both came with a power supply, was just wondering if I can power these straight from the mains.Thanks.

author: alanb
author_rank: Frequent Contributor
timestamp: October 25, 2017, 02:42:03 pm
content: Hi TomBoth of these instruments are designed to run off the mains. I would be interested to know what the power supply is that you have received? It could possibly be an isolation transformer to power the device you are testing. Can you post a picture?

author: alanb
author_rank: Frequent Contributor
timestamp: October 25, 2017, 02:46:19 pm
content: One other possibility is that the scope and signal generator were for the non UK market (110V) and the power supply is a 240 - 110 transformer.

author: tombaxter97
author_rank: Contributor
timestamp: October 25, 2017, 02:58:45 pm
content: Sorry, I've just realised that I was a bit careless with my question (probably still excited about the scope being delivered a day early) by power supply I just meant a power cable with a plug on. The only only reason I ask is that I have saw a lot about lab power supply but I suppose if I can just plug these straight into the wall that may be something for the future.Thanks for the help.

author: tombaxter97
author_rank: Contributor
timestamp: October 25, 2017, 03:05:38 pm
content: I'm guessing plugging either into a 4 plug extension cable isn't a good idea?

author: Ian.M
author_rank: Super Contributor
timestamp: October 25, 2017, 04:12:30 pm
content: Actually, using a multi-way extension cable can be a very good idea - it ensures that all the Grounds are connected together as close as possible to the test equipment and minimises the risk of high circulating currents in any ground loops that are formed when you connect multiple items of test equipment to the device under test.If you plug them into wall outlets with a common back-box, that's also acceptable as there will either be a common ground or the grounds will be tied together.The case you really want to avoid is powering different items of test gear with three wire mains leads and grounded inputs or outputs from different mains circuits, especially if there are high ground currents on either circuit.N.B. *NEVER* use an isolation transformer to power, or other method of breaking the supply ground connection to, any item of test equipment that has a three wire mains lead unless the operating manual (or other statement from the manufacturer) specifically permits operation without a ground connection.

author: james_s
author_rank: Super Contributor
timestamp: October 25, 2017, 06:27:00 pm
content: Assuming they have a standard mains connector on them, just plug them in. Straight into the wall or into an appropriate extension cord or power strip is fine. If you live in 240V land especially, take a look at the voltage selection switch if it has one and make sure it's set to the correct voltage.A lab power supply is a separate instrument, it is not for powering test gear. Generally it will produce one or more DC voltages used to power devices and circuits you are working on.

author: tombaxter97
author_rank: Contributor
timestamp: October 25, 2017, 07:02:41 pm
content: Thanks for getting back so quick, was just a bit apprehensive about blowing the things before I've even got to use them.

author: Ian.M
author_rank: Super Contributor
timestamp: October 25, 2017, 07:34:41 pm
content: Until you've gained some experience, don't use your HM605 or PM5131 on any circuit that isn't either powered by a low voltage current limited isolated PSU (e.g. a proper bench PSU or a wallwart) or by smaller primary cell batteries (and not by C or D cells or high current LiPO, NiCd,NiMH or Lead Acid batteries). Also, don't connect the HM605's probe ground clip or the PM5131 BNC lead ground clip to anything except the circuit's signal ground/0V rail (if they aren't the same, stop and ASK!). This minimises the risk of melting your test leads and damaging your test equipment.Mandatory viewing for new 'scope' users:https://www.eevblog.com/2012/05/18/eevblog-279-how-not-to-blow-up-your-oscilloscope/

author: james_s
author_rank: Super Contributor
timestamp: October 27, 2017, 08:54:58 pm
content: Quote from: tombaxter97 on October 25, 2017, 07:02:41 pmWell if in doubt, it's always better to ask rather than make assumptions and blow something up.