atkelar | Workshop Project #14 - ESI 250DE Impedance Bridge @atkelar | Uploaded February 2022 | Updated October 2024, 16 hours ago.
It was in late 2021 when I was browsing ebay for a decent LRC (or RLC) metering device. Originally, I thought I'd go for a cheap-ish digital one, but then this little gem of a retro device popped up for rather cheap. It was cheap mostly because it was untested and had at least one stuck knob. Sounds like a challenge to me!
The device itself is based on a Wheatstone / Wien bridge circuit and allows very precise measurements of resitsors, capacitors and inductors: R, C and L. I always mix up the sequence of these letters in the product names and I'm sure there are multiple versions out there... LRC? RLC? Doesn't really matter: all three of them!
I did the usual recapping and cleaning, although internally not much cleaning was needed. Wow. It looked brand new inside!
I am also not sure if the device originally came with a cover; the case has attachment points for something along these lines on the side, but the manual doesn't indicate one way or the other. Making one might be a neat build project at a later time maybe. I'll keep it on my list of things to do!
It would be interesting to see how accurate the thing is. If I ever get to some calibration lab, I'll be sure to bring it along. All test measurements were agreeing in magnitude and first significant digits with my other means of checking them. The 3rd and 4th digit is where I can't confirm anthing sadly. But since I didn't change anything on the precision resistors and the reference cap, I'd assume it's at least in the "more than OK for hobby use" range.
And before you ask: yes, the "restored by Atkelar" sticker is ever so slightly crooked again. At some day I might get lucky and manage the proper alignment before the sticky side starts to stick to a freshly painted case.
0:00 Intro / Presentation / Inspection
1:31 No Batteries?
2:05 Open Case / Shiny! / Strategy
3:16 Golden Tin Can? / Binding Posts
4:28 Triple Potentiometer
5:16 "Dekastat(tm)"
5:46 Cleaning / BNC / GAIN potentiometer
6:57 D-Q Potentiomater Assembly / Recapping P2P
7:42 Strange Capacitors
8:21 Delete Charger / Battery Tube
9:51 Case Refurbishing
10:42 Reassembly!
11:40 D-Q deba-q-le...
12:22 D-Q wiper adjustment / Tidbits and Dials
13:17 Chassis Layer 2
13:55 Test #1: Batter Check
14:11 Bridge Circuit, Rough Theory
15:36 Resistor...
16:21 Capacitor...
17:18 Inductor Measurement
17:38 D/Q and ESR math overview
18:57 Case Finish
19:51 Done! Overview / Bye / Credits / Outtakes
Music:
My Train's A Comin'
Unicorn Heads
(YouTube Audio Library)
You can support me on Ko-Fi: ko-fi.com/atkelar
Useful links that I found via Google that were helpful for this project:
Wheatstone Bridge: en.wikipedia.org/wiki/Wheatstone_bridge
Wien Bridge: en.wikipedia.org/wiki/Wien_bridge
Historical account for the Wheatstone Bridge: youtube.com/watch?v=yCURsJoXHfs
Formulas around capacitors: xtronics.com/wiki/Capacitors_and_ESR.html
And the manufacturer: en.wikipedia.org/wiki/Electro_Scientific_Industries
Homepage: esi.com
It was in late 2021 when I was browsing ebay for a decent LRC (or RLC) metering device. Originally, I thought I'd go for a cheap-ish digital one, but then this little gem of a retro device popped up for rather cheap. It was cheap mostly because it was untested and had at least one stuck knob. Sounds like a challenge to me!
The device itself is based on a Wheatstone / Wien bridge circuit and allows very precise measurements of resitsors, capacitors and inductors: R, C and L. I always mix up the sequence of these letters in the product names and I'm sure there are multiple versions out there... LRC? RLC? Doesn't really matter: all three of them!
I did the usual recapping and cleaning, although internally not much cleaning was needed. Wow. It looked brand new inside!
I am also not sure if the device originally came with a cover; the case has attachment points for something along these lines on the side, but the manual doesn't indicate one way or the other. Making one might be a neat build project at a later time maybe. I'll keep it on my list of things to do!
It would be interesting to see how accurate the thing is. If I ever get to some calibration lab, I'll be sure to bring it along. All test measurements were agreeing in magnitude and first significant digits with my other means of checking them. The 3rd and 4th digit is where I can't confirm anthing sadly. But since I didn't change anything on the precision resistors and the reference cap, I'd assume it's at least in the "more than OK for hobby use" range.
And before you ask: yes, the "restored by Atkelar" sticker is ever so slightly crooked again. At some day I might get lucky and manage the proper alignment before the sticky side starts to stick to a freshly painted case.
0:00 Intro / Presentation / Inspection
1:31 No Batteries?
2:05 Open Case / Shiny! / Strategy
3:16 Golden Tin Can? / Binding Posts
4:28 Triple Potentiometer
5:16 "Dekastat(tm)"
5:46 Cleaning / BNC / GAIN potentiometer
6:57 D-Q Potentiomater Assembly / Recapping P2P
7:42 Strange Capacitors
8:21 Delete Charger / Battery Tube
9:51 Case Refurbishing
10:42 Reassembly!
11:40 D-Q deba-q-le...
12:22 D-Q wiper adjustment / Tidbits and Dials
13:17 Chassis Layer 2
13:55 Test #1: Batter Check
14:11 Bridge Circuit, Rough Theory
15:36 Resistor...
16:21 Capacitor...
17:18 Inductor Measurement
17:38 D/Q and ESR math overview
18:57 Case Finish
19:51 Done! Overview / Bye / Credits / Outtakes
Music:
My Train's A Comin'
Unicorn Heads
(YouTube Audio Library)
You can support me on Ko-Fi: ko-fi.com/atkelar
Useful links that I found via Google that were helpful for this project:
Wheatstone Bridge: en.wikipedia.org/wiki/Wheatstone_bridge
Wien Bridge: en.wikipedia.org/wiki/Wien_bridge
Historical account for the Wheatstone Bridge: youtube.com/watch?v=yCURsJoXHfs
Formulas around capacitors: xtronics.com/wiki/Capacitors_and_ESR.html
And the manufacturer: en.wikipedia.org/wiki/Electro_Scientific_Industries
Homepage: esi.com
