2 layers58 × 110 mm
2 layers60 × 80 mm
Keithley1950
openscopeproject/Keithley19509Keithley 195A DMM Option 1950
- Size
- 60 × 80 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 92
- Nets
- 88
- Pads
- 323
- Tracks, vias
- 879, 83
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 5 (file 20171130)
- Created
- 19 Jan 2020
- Updated
- 19 Jan 2020
Overview
Keithley1950 is an open-source printed circuit board by openscopeproject, from the openscopeproject/Keithley1950 repository on GitHub. It is a 2-layer board of 60 × 80 mm with 92 parts on 88 nets, routed with 879 tracks and 83 vias.
It is built around the TLE2072ID, AD8436ACP and 74HC4094D, with the LM339, ULN2003 and S3M among its other parts. Its parts include 28 resistors, 24 capacitors, 8 transistors, 7 ICs and 7 diodes.
Main components
8
TLE2072ID
SOIC-8-19V~19V -40℃~+85℃ 1.35mA 17nV/√Hz@1kHz 2 3.2uV/℃ 340uV 35V/us 45mA 5nA 70dB 9.4MHz Built-in compensation SOIC-8 FET Input Amplifiers ROHSTexas InstrumentsFET Input Amplifiers
AD8436ACP
QFN20Low Cost, Low Power, True RMS-to-DC Converter, Output Offset Voltage ±0.5 mV (-40°C to +125°C)Analog DevicesUncategorised
74HC4094D
SO-16-40℃~+125℃ 1 2V~6V 74HC 8 Serial-to-Serial or Parallel Tri-State SOIC-16 Shift Registers ROHSNexperiaShift Registers
LM339
SOP-140℃~+70℃ 1.1mA 1.5mV 150ns 2.3nA 2V~32V 32V 57nA DTL、TTL、CMOS Four channels Open Collector SOP-14 Comparators ROHSJSMSEMIComparators
ULN2003
SOP-161.1V@250uA,100mA 25pF 2V 30V 500mA 50uA 50uA Seven channels SOP-16 Darlington Transistor Arrays ROHSBLDarlington Transistor Arrays
S3M
SMC(DO-214AB)-65℃~+150℃ 1 Independent 1.15V@3A 10uA@1kV 1kV 3A SMC(DO-214AB) Diodes - General Purpose ROHSDiodes IncorporatedDiodes - General Purpose
MMBFJ111
SOT-23-55℃~+150℃ 1 N-channel 20mA 30Ω 350mW 35V 3V N-Channel SOT-23 JFETs ROHSonsemiJFETsMMBT3906
SOT-23-55℃~+150℃ 1 PNP 100 100nA 200mA 200mW 300MHz 300mV 40V 5V PNP SOT-23 Bipolar (BJT) ROHSTWGMCBipolar (BJT)
README
README.mdKeithley 195A DMM Option 1950
Keithley Instruments 195A Digital Multimeter is a 5½ digit resolution 200 000 count instrument that was manufactured in the 80's, possibly early 90's. It was available in two configurations: base model that only had DC Volts and Ohms measurements and model with 1950 option, which added DC/AC Amps and AC TRMS Volts measurements.
Keithley DMM line has long replaced 195/196/199 series with newer models but these still show up on Ebay and other outlets and they offer great performance for reasonable prices. Unfortunately most of the 195A models available online are the ones without 1950 Option.
This project aims to recreate the 1950 Option PCB and circuitry using modern components.
In the process some upgrades and some compromises were made. For example this version of 1950 option board is based on AD8436 trms chip that along with newer opamps provides higher bandwidth and better overall specs than much older AD536 of the original. On the other hand cheaper shunt resistors are used (because of their availability) with worse drift and tempco characteristics.
High voltage operation using the new board is also NOT recommended or tested.
BOM
See bom for this board generated by InteractiveHtmlBom plugin for KiCad.
Schematic
3D render
Pictures
End result installed in the meter
Original board next to new version
Close up of rev A board with Genuine Bodge™ visible on the left
Parts
92| Qty | Value | Footprint | References |
|---|---|---|---|
| 10 | .1uF | Capacitor_SMD:C_0603_1608Metric | C5, C6, C8, C11, C13, C14, C15, C16, C17, C18 |
| 7 | S3M | Diode_SMD:D_SMB | D1, D2, D3, D4, D5, D6, D7 |
| 6 | 10k | Resistor_SMD:R_0805_2012Metric | R1, R2, R16, R18, R22, R27 |
| 5 | 100k | Resistor_SMD:R_0805_2012Metric | R4, R7, R8, R11, R28 |
| 5 | MMBFJ111 | Package_TO_SOT_SMD:SOT-23 | Q1, Q2, Q3, Q4, Q7 |
| 4 | Relay_SP2P | Relay_THT:Relay_SPST_StandexMeder_SIL_Form1A | K1, K2, K4, K5 |
| 3 | 47uF | Capacitor_SMD:CP_Elec_6.3x5.9 | C1, C2, C3 |
| 3 | MMBT3906 | Package_TO_SOT_SMD:SOT-23 | Q5, Q6, Q8 |
| 3 | MountingHole_Pad | MountingHole:MountingHole_3.2mm_M3_Pad_Via | H1, H2, H3 |
| 3 | Relay_SP3P | Relay_THT:Relay_SPDT_SANYOU_SRD_Series_Form_C | K3, K6, K7 |
| 3 | TestPoint | TestPoint:TestPoint_Pad_D2.5mm | TP1, TP2, TP3 |
| 2 | 1M | Resistor_SMD:R_0805_2012Metric | R25, R26 |
| 2 | 5pF | project:MURATA_TZ03 | C21, C24 |
| 2 | TLE2072 | Package_SO:SOIC-8_3.9x4.9mm_P1.27mm | U1, U7 |
| 1 | 0.1uF | Capacitor_THT:C_Rect_L18.0mm_W5.0mm_P15.00mm_FKS3_FKP3 | C23 |
| 1 | 0R1 | project:R_2512_With_10mm_axial | R17 |
| 1 | 10M | Resistor_SMD:R_0805_2012Metric | R19 |
| 1 | 10uF | Capacitor_Tantalum_SMD:CP_EIA-3528-21_Kemet-B | C7 |
| 1 | 10uF | Capacitor_SMD:C_0805_2012Metric | C9 |
| 1 | 110pF | Capacitor_SMD:C_0805_2012Metric | C20 |
| 1 | 1uF | Capacitor_SMD:C_0805_2012Metric | C10 |
| 1 | 27k | Resistor_SMD:R_0805_2012Metric | R21 |
| 1 | 2k | Resistor_SMD:R_0805_2012Metric | R20 |
| 1 | 3.3uF | Capacitor_SMD:C_0805_2012Metric | C12 |
| 1 | 3k | Resistor_SMD:R_0805_2012Metric | R24 |
| 1 | 430R | Resistor_SMD:R_0805_2012Metric | R5 |
| 1 | 43R | Resistor_SMD:R_0805_2012Metric | R9 |
| 1 | 470R | Resistor_SMD:R_0805_2012Metric | R3 |
| 1 | 470pF | Capacitor_SMD:C_0805_2012Metric | C4 |
| 1 | 47R | Resistor_SMD:R_0805_2012Metric | R6 |
| 1 | 47pF | Capacitor_SMD:C_0805_2012Metric | C22 |
| 1 | 4R3 | Resistor_SMD:R_0805_2012Metric | R12 |
| 1 | 4R7 | Resistor_SMD:R_0805_2012Metric | R10 |
| 1 | 5R1 | Resistor_SMD:R_2512_6332Metric | R13 |
| 1 | 610pF | Capacitor_SMD:C_0805_2012Metric | C19 |
| 1 | 74HC4094 | Package_SO:SOIC-16_3.9x9.9mm_P1.27mm | U6 |
| 1 | 74LS138 | Package_SO:SOIC-16_3.9x9.9mm_P1.27mm | U3 |
| 1 | AD8436 | Package_SO:QSOP-20_3.9x8.7mm_P0.635mm | U4 |
| 1 | Conn_01x02 | TerminalBlock_Phoenix:TerminalBlock_Phoenix_PT-1,5-2-5.0-H_1x02_P5.00mm_Horizontal | J3 |
| 1 | Conn_01x03 | TerminalBlock_Phoenix:TerminalBlock_Phoenix_PT-1,5-3-5.0-H_1x03_P5.00mm_Horizontal | J2 |
| 1 | Conn_01x14 | Package_DIP:DIP-14_W7.62mm_Socket_LongPads | J1 |
| 1 | DNP | Resistor_SMD:R_0805_2012Metric | R23 |
| 1 | LM339 | Package_SO:SOIC-14_3.9x8.7mm_P1.27mm | U2 |
| 1 | LOGO | project:osp-logo | LOGO*** |
| 1 | R43 | Resistor_SMD:R_2512_6332Metric | R15 |
| 1 | R47 | Resistor_SMD:R_2512_6332Metric | R14 |
| 1 | TestPoint | TestPoint:TestPoint_THTPad_D1.5mm_Drill0.7mm | TP4 |
| 1 | ULN2003 | Package_SO:SOIC-16_3.9x9.9mm_P1.27mm | U5 |
Questions
How big is the Keithley1950 PCB?
It measures 60 × 80 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Keithley1950 use?
92 parts, built around the TLE2072ID, AD8436ACP, 74HC4094D and LM339. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Keithley1950 KiCad files?
From the openscopeproject/Keithley1950 repository on GitHub, at the commit this page was made from: the board is Keithley1950.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Keithley1950 design in my own project?
Its repository states no licence, so its author keeps all rights: ask openscopeproject before reusing the design.
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