Precision Resistor + Capacitor Box: advice and criticism welcome - Page 1
Forum section: electronics / projects

author: jake900
author_rank: Newbie
timestamp: January 22, 2018, 10:48:51 pm
content: I am making a box with precision resistors and caps, please check out the bill of materials below. I have a few questions relating to the design and I welcome any input in case I have missed something. ThanksBOM - Numbers quoted are farnell order numbersVishay Resistors10R -28205150.01% 0.2ppm/c £16.66 (4-wire)100r -28205040.01% 0.2ppm/c £12.98 (2-wire)1k -28205060.01% 0.2ppm/c £12.98 (2-wire)10k -28205120.01% 0.2ppm/c £12.98 (2-wire)100K -28204950.01% 2ppm/c £15.97 (2-wire)2 are not in stock until mid-feb, and 2 are not in stock until mid-march.Silver Mica Caps10pF -2333472+/-0.5pF100pF -12648801%1nF -12648901%10nF -Ebay SSG 0.5% 10,000pF100nF -Ebay SSG 0.5% 50,000pF- will use a pairI don't really know anything about precision capacitors - these are about the best I could find.EnclosureMC001133 -2544963Die Cast, Aluminium Alloy, 75 mm, 200 mm, 120 mmI plan on using 4mm shrouded sockets, and having one side of all the resistors common. The 10r is 4-wire but I would like to have just one further socket for each of the other values. I aim to do point-to-point soldering with all but the highest values of resistor.Questions:Can I make one side of all the caps share a common socket with the resistors or will excessive wiring affect low cap values?Would sockets like these be suitable?1085482I really don't know much about contact materials, seebeck effect etcWhat type of wire should I use for the common?Can anyone recommend a 1 Meg resistor of comparable performance?Does the enclosure seem suitable? I was planning to put this in a 19in enclosure with a voltage and current reference also - but as that probably wont happen for a while I will use something smaller.I know that I have not given any specifications for the design as a whole but I just want to make sure that the connectors and wiring are good enough for the resistors not to negatively impact their specs.Let me know if I have overlooked anything, thanks.

author: ocw
author_rank: Regular Contributor
timestamp: January 23, 2018, 12:00:15 am
content: I have many of the same or similar resistors.QuoteI have USF340-1.00M-0.01%-5PPM and VHA4121M0000S 0.001% 2.0 PPM/C 1M resistors. I also have a USF340-10.0M-0.01%-T-5PPM 10M resistor. It gets expensive to go for greater thermal stability for those higher values. I have a fair number of other 0.01% and a few 0.005% resistors.I have found that having all 1.0 decade resistors often does not properly measure the meter's linearity. Using the same integer decade resistors shows its basic accuracy plus the accuracy of its dividers, etc. You need some values in-between like around 3 or 2 and 4.7 to see if the meter has a linearity problem. I've often found that 1k, 10k and 100k measurements (as an example) often have the same accuracy while my 2.5k, 5k, 25.14k, 49.9k and 277.8 k 0.01% resistor measurements have less precise measurement accuracy.The same is true with capacitance. And, depending on the meter being evaluated, added inaccuracy will occur when measuring small value capacitors unless the meter is connected directly to the capacitor.I also have a four lead Y092610R0000T9L 10 ohm resistor. You need to have all four of its leads available for precision use of it. For resistance accuracy use almost direct connection is required.I keep all of my precision reference components separate to eliminate any multi-component and wiring contamination.

author: jake900
author_rank: Newbie
timestamp: January 24, 2018, 08:30:33 pm
content: Quote from: ocw on January 23, 2018, 12:00:15 amThats a good point, on the decade values - thank you, I will also order a 5k and 20k of the same series for now2820510&2820507. I have found one of the 1megs that you have on RS and will order that too,888-5152I definitely want these in a box with 4mm sockets, but I will test them in different configurations first. I will have the actual value written next to each as well. Using calibrated current source and DMM (transmille 3050 & fluke 8846). I do not actually have anything which can accurately measure the capacitors unless I can derive the measurement from some other way - another thing to look into.thanks for your response