Yokogawa 2755 Wheatstone Bridge  - Page 1
Forum section: electronics / testgear

author: pyroesp
author_rank: Regular Contributor
timestamp: September 26, 2016, 12:39:26 am
content: Picked up something on ebay and got this Yokogawa 2755 Wheatstone bridge, for free!I haven't powered it up or tried it yet, but here are some pictures (images are a bit big for the forum.):http://imgur.com/a/SUXqhMy uncalibrated HP3478A multimeter in 4W mode reads:9.999k for the 10k resistor (x1000 switch set to 10)999.69Ohm for the 1k resistor (x100 switch set to 10)99.767Ohm for the 100 Ohm resistor (x10 switch set to 10)9.7738Ohm for the 10 Ohm (x1 switch set to 10)0.7855Ohm for the 1 Ohm (x1 switch set to 1)BTW, those switches feel amazing !

author: Vgkid
author_rank: Super Contributor
timestamp: September 26, 2016, 03:08:48 am
content: Nice portable wheatstone bridge. Nice that it works, though you might have to work on your measurement results for the lower resistance ranges...Here is a teardown of mine.https://www.eevblog.com/forum/metrology/ln-4232-wheatstone-bridge/

author: radhaz
author_rank: Regular Contributor
timestamp: September 26, 2016, 03:22:52 am
content: Nice. What can it be used for? Decade box I know, but galvanometer?

author: Vgkid
author_rank: Super Contributor
timestamp: September 26, 2016, 04:14:50 am
content: ^^^ Those are 2 possible uses for them today, unless you want to use them. Though if it was a double ratio(kelvin) bridge, they are stll useful for measuring low resistances.

author: pyroesp
author_rank: Regular Contributor
timestamp: September 26, 2016, 10:40:30 am
content: Quote from: Vgkid on September 26, 2016, 03:08:48 amI have nothing to calibrate my DMM yet. It also needs a good washing and probably new caps here and there.Quote from: radhaz on September 26, 2016, 03:22:52 amIt's a resistance meter. If you read the back of the unit, it has instructions on how to use it, and then calculate the resistor connected on the Rx terminals.Rx = (MULTIPLY FACTOR) x (Total of MEASURING DIALS) OhmsI'll try powering it up tonight and measure a few resistors.

author: Vgkid
author_rank: Super Contributor
timestamp: September 26, 2016, 08:53:04 pm
content: Quote from: pyroesp on September 26, 2016, 10:40:30 amYour meter should be fine. Measure from RX to GA. You will need to figure out which RX terminal to use, else you will be measuring the range resistor. Make sure the switches(ga/ba) are open.

author: barry14
author_rank: Regular Contributor
timestamp: September 26, 2016, 11:23:22 pm
content: This is similar to bridges built by Leeds & Northrup for many years. Their main drawback is that the sensitivity drops off very rapidly as the unknown resistance differs from the main bridge resistors. Usually these are in the 1 -10 kilohm range. Thus you will be able to get a 4 digit balance for unknowns in that range but progressively less as the unknown gets either higher or lower. At the extremes (x.001 and X1000), you will be lucky to get 2 digit balancing. If you look at the specifications for this type of bridge, the accuracy drops off significantly as the unknown requires use of other than the 1X range.

author: pyroesp
author_rank: Regular Contributor
timestamp: September 27, 2016, 05:55:06 am
content: This is the accuracy of the meter:Range, ±0.1% of reading on 100? to 100k? Range, ±0.3% of reading on 10? to 1M? Range, ±0.6% of reading on 1? to 10M? RangeHaven't tried it yet (because of work and stuff), but I'm sure it will be a PITA to set at the lower ranges, like barry14 said.I'm thinking of buying a DMMCheck plus from VoltageStandard, for my DMM.