Contents
- Introduction
- EM A10 Nanovolt amplifier overview
- Keithley 1801 Nanovolt amplifier overview
- Interface module design
- Preamp calibration
- Experiment setup
- Test results
- Conclusion
Introduction
EM Electronics is a known name in very low signal voltage and current measurement applications.
EM A10 Nanovolt amplifier overview
There is overview page on EM site covering A10 specifications and features
Exterior
Interior
Keithley 1801 Nanovolt amplifier overview
Few years after this project started, we finally got hands on actual Keithley 1801 preamp. Compare it to EM A10. Purple board is on the left top is custom adapting PCBA for A10 with onboard gain resistors, calibration circuit and low-noise linear regulators.
Bottom side have sticker with datecode. According this 0804 mark, this 1801 manufactured around week 4 year 2008, 11 years ago.
It’s not all perfect however, LO post is slightly bend, making nuts very hard to turn. :(
Remove top four screws allow us to remove the top lid for PCBA overview.
It’s clearly made by EM Electronics, with little A10Ke marking in corner, confirming idea of origins as A10 amplifier + onboard gain resistors and filter caps to make it all-in-one solution for Keithley 2001/2002 control.
Interface module design, connection to DMM
Sensitive amplifier, such as EM A10 require special care in every aspect of application and operation. Accurate measuring nanovolt-level signals is more state of art, rather than usual engineering toss-all-parts together and power it on. All things matter, there are no insignificant details.
Good example of usage scenario and setup is covered in Keithley’s instruction manual for Model 1801. To be precise, Model 1801 is older version of EM A10 amplifier, with few extra things in it, such as gain switching and selectable filtering caps. Original Model 1801 kit (consists of Model 1801 preamplifier head, RJ50 interface cable and addon power supply card for K2001/K2002 DMMs) is long obsolete, and not possible to buy from Keithley or distributors, so we have no choice left but to design very own interface board to connect A10.
Example gain settings and input/output voltages
| Range at input | Input signal | GAIN | Output | RFB | RGAIN | Vout |
|---|---|---|---|---|---|---|
| 1 mV | 2.00-3 | 1000 | 2.0000 | 1 Ω | 999 Ω | 2.000000 V |
| 100 µV | 2.00-4 | 10000 | 2.0000 | 1 Ω | 9999.00 Ω | 2.000000 V |
| 10 µV | 2.00-5 | 100000 | 2.0000 | 1 Ω | 99999.0 Ω | 2.000000 V |
| 1 µV | 2.00-6 | 100000 | 2.00-1 | 1 Ω | 99999.0 Ω | 200.0000 mV |
| 100 nV | 2.00-7 | 100000 | 2.00-2 | 1 Ω | 99999.0 Ω | 20.0000 mV |
| 10 nV | 2.00-8 | 100000 | 2.00-3 | 1 Ω | 99999.0 Ω | 2.0000 mV |
| 1 nV | 2.00-9 | 1000000 | 2.00-4 | 1 Ω | 999999.0 Ω | 2.0000 mV |
| 100 pV | 2.00-10 | 1000000 | 2.00-5 | 1 Ω | 999999.0 Ω | 0.2000 mV |
Of course it’s easier to just power A10 amplifier with ±8.5VDC supply and connect it’s output to your favorite DMM, but we were interested in making nice usable kit, since I have multiple Keithley Model 2001 and Model 2002 DMMs. DMM firmware (Model 2001 must have B-version firmware to support preamp) already have support for 1801 preamp, and show proper ranges information.
Module specification
After review of existing Keithley 1801 and Model 2182, 182 nanovoltmeters specs it was decided to have next key features in this design:
- Natively support Keithley 1801 head amplifier
- Support EM A10 head amplifier
- Provide isolated clean supply voltage (±8.5VDC for 1801, +/-6VDC for A10)
- Provide isolated digital supply voltage (±5.0VDC for 1801, no need for A10)
- Support Keithley’s TR285 and TR286 transformers for push-pull DC/DC
- 24Cxx EEPROM chip for calibration data storage (used natively by Keithley 2001/2002 firmware)
- Onboard PCB temperature sensor
- Digital control via optical isolation for filter/gain (for 1801)
- Virtual ground supply/bias circuit (for 1801)
- Faraday cage for isolated section
- Mechanical footprint to fit Keithley option slot
- Hand-soldering friendly component selection, minimum SMD size 0603, only 4 QFN packages
- Battery-powered option for best noise performance
Worth to note, that Keithley original transformers used in Model 1801 power supply card are possible to order, but price for them is extraorbitant, around 600 $USD. So while our design still support their use, second plan B option is also made to support usual push-pull converter using market transformer Eaton Bussmann CTX02-13665 and Linear LTC3439EME push-pull converter. Both boards are referenced in further text as XA1 for discrete push-pull with Keithley transformers and XA2 with LTC3439 option.
Schematics blocks
Original manual from 1801 preamp have schematics for power supply module, so we can use basic idea and design around it, using modern quality components for SMT and circuit design. We did contact Keithley in attempt to buy Model 1801, but got feedback that unit is obsolete and not available anymore. Also few extra features are added, not present in original design. It would be clear to note, that module and design discussed below is not a clone or simple copy of original 1801.
Main schematic blocks:
Keithley add-on card DIN 32-pin connector (on left) providing digital interface and +5V supply to whole module. Serial bus is connected to 4094 shift register, which used to control switching for gain and filtering capacitors on head. Control signals are isolated via U9 PSL2501 optocoupler array.
This part resembles original Keithley 1801 module card, as we want to be compatible with firmware controls.
Calibration constants and data is stored in I2C EEPROM, in our case 24C02 or bigger device. Optional resistors are available to customize address. I2C address also routed to DIP-switch.
Power supervision and reset generation, handled by TL7705, similar to Keithley circuitry here.
Isolated side is simply driving switches at head, with pull-up/pull-downs to isolated ±8.5VDC supplies.
Keithley isolation transformers designed for push-pull topology, so we used 74HC74 DFF-based oscillator for 9.6kHz, with further divider by 2 to get differential complimentary drive at 4.8kHz for pair of N-channel MOSFETs. Stable capacitors 82nF and 988 Ω resistors being used to provide necessary stability and accuracy.
C30 acting as bulk capacitor to provide local transient supply and C54 is optional damper capacitor.
Output from push-pull DC/DC converter is rectified and filtered by VD1,VD2 diode bridges and output RC circuits. Damper networks R58,C50,R43,C31 are optional to use, depends on actual testing.
Positive isolated +5VDC for K1801 head logic supply generated by very low noise Linear LT3042 LDO in 10-DFN package. This LDO with current reference is adjustable in wide range by single resistor R45, and able to provide up to 200mADC of current with only 0.8µV noise. This regulator not needed for EM A10 head.
Negative isolated -5VDC for K1801 head logic supply is generated by similar low noise Linear LT3090 LDO. This device with current reference is adjustable in range by single resistor R47, and configured for maximum current up to 200mADC via R48. This regulator not needed for EM A10 head.
Main isolated low noise ±8.5VDC supply for analog part of head is generated from very low noise Linear LDOs, LT3042 and LT3090. Circuitry is same as ±5VDC supplies. If battery power instead of push-pull transformer converter used, this supplies provide input power for ±5VDC LDOs, otherwise everything isolated.
Output Molex connector is NOT pin-pin compatible to Keithley 1801 module, so we use own cable pinout to connect with nanovolt amplifier head. Output signal from amplifier routed to pin 3, which is shielded by low-impedance guarded ground to provide best noise isolation. Protection TVS-diodes D26,D27 near connector provide additional protection from overvoltage/reverse polarity for preamplifier head. Output is quality SMA port with copper terminals to minimize EMF and provide coax output.
Additional circuitry
Maxim MAX6610 temperature sensor and auxiliary reference output, powered from Keithley’s digital +5V supply. Output are routed to SMA footprints.
Battery option. Requires ±12V-16VDC input, isolated from mains or Keithley DMM chassis. D28 and D29 protect module input from overvoltage/reverse polarity.
DIP-switch is implemented to allow using module standalone, without Keithley DMM or for debug/testing purposes.
Non-isolated digital signals are provided at Tektronix P6860 logic analyzer footprint for easy and quick probing.
Ground current compensation provide low-impedance drive for DC offset cancellation. This part is derived from K1801 power supply module, and may be optional.
Full PDF-schematics, Keithley discrete transformer version, XA1
XA2 module version is exactly same except 74HC74 push-pull drive and Keithley transformers replaced with off-the-shelf DC-DC solution, based on Linear LT3439 and CTX02-13665 push-pull transformer to output isolated ±12VDC @250mADC.
Full PDF-schematics, Linear LT3439 + CTX02-13665 version, XA2
Layout design
TBD
Module BOM and parts selection
Module for original Keithley transformers. All BOM prices are from Digikey store.
| Description | Vendor | Vendor P/N | QTY | Cost, $USD | Total |
|---|---|---|---|---|---|
| CAP CER 100nF 35V X7R 0603 | Taiyo Yuden | GMK107B7104KAHT | 24 | 0.184 | 4.416 |
| CAP CER 47nF 50V NP0 1206 | Murata Electronics North America | GRM31M5C1H473FA01L | 1 | 1.01 | 1.01 |
| CAP TANT 100UF 20V 10% 2917 | Vishay Sprague | TR3D107K020C0080 | 2 | 1.551 | 3.102 |
| CAP CER 1500PF 630V C0G 1206 | TDK Corporation | CGA5H4C0G2J152J115AA | 1 | 0.28 | 0.28 |
| CAP CER 10UF 35V X7R 1206 | Taiyo Yuden | GMK316AB7106KL-TR | 4 | 0.49 | 1.96 |
| CAP CER 0.47UF 50V X7R 0603 | TDK Corporation | C1608×7R1H474M080AE | 4 | 0.304 | 1.216 |
| CAP CER 2.2UF 50V X7R 1206 | Murata Electronics North America | GRJ31CR71H225KE11L | 4 | 0.318 | 1.272 |
| CAP CER 1500PF 630V C0G 1206 | TDK Corporation | CGA5H4C0G2J152J115AA | 1 | 0.28 | 0.28 |
| CAP CER 0.022UF 630V C0G 1210 | TDK Corporation | C3225C0G2J223J230AA | 1 | 1.025 | 1.025 |
| CAP CER 0.082UF 50V NP0 1206 | Murata Electronics North America | GRM31C5C1H823JA01L | 2 | 0.692 | 1.384 |
| CAP CER 1000PF 1KV NP0 1206 | Kemet | C1206C102JDGACTU | 1 | 0.871 | 0.871 |
| IC REG LDO ADJ 0.2A 10DFN | Linear Technology | LT3042EDD#PBF | 2 | 4.9 | 9.8 |
| IC REG LDO NEG ADJ 0.6A 10DFN | Linear Technology | LT3090EDD#PBF | 2 | 4.65 | 9.3 |
| IC OPAMP GP 8MHZ 8SO | Linear Technology | LT1007CS8#PBF | 2 | 4.15 | 8.3 |
| IC OPAMP GP 50MHZ 8SOIC | Analog Devices Inc. | AD847JRZ | 1 | 8.39 | 8.39 |
| IC 4.55V SUPPLY MONITOR 8-SOIC | Texas Instruments | TL7705ACDR | 1 | 0.51 | 0.51 |
| SENSOR TEMP RATIOMETRIC SOT23-6 | Maxim Integrated | MAX6610AUT+T | 1 | 2.117 | 2.117 |
| IC D-TYPE POS TRG DUAL 14SOIC | NXP Semiconductors | 74HC74D,653 | 1 | 0.29 | 0.29 |
| IC EEPROM 2KBIT 1MHZ 8SOIC | Atmel | AT24C02D-SSHM-T | 1 | 0.213 | 0.213 |
| IC REGISTER BUS 8STAGE 16SOIC | NXP Semiconductors | 74HC4094D,653 | 1 | 0.387 | 0.387 |
| OPTOISOLTR 5KV 4CH TRANS 16-SMD | ON Semiconductor | PS2501L-4 | 1 | 1.734 | 1.734 |
| DIODE BRIDGE 800V 1.5A 4-SMD | Fairchild Semiconductor | DF08S | 2 | 0.425 | 0.85 |
| DIODE GEN PURP 75V 150MA SOD523 | Micro Commercial Co | 1N4148X-TP | 2 | 0.125 | 0.25 |
| CONN HEADER 10POS .100 R/A SMD | Molex, LLC | 15912105 | 1 | 5.343 | 5.343 |
| TERM BLK 3POS 5.08MM SPRING GRN | Phoenix Contact | 1790296 | 1 | 2.557 | 2.557 |
| CONN DIN RCPT 32POS DUAL RT ANG | Hirose Electric Co Ltd | PCN10C-32S-2.54DS(72) | 1 | 5.911 | 5.911 |
| Transformer | Keithley Instruments | TR286B | 1 | 393 | 393 |
| Transformer | Keithley Instruments | TR285B | 1 | 193 | 193 |
| SW DIP EXT RCKR SEALED 8POS 30V | Grayhill Inc. | 76SB08ST | 1 | 1.441 | 1.441 |
| LED GREEN CLEAR 1206 SMD | Wurth Electronics Inc | 150120GS75000 | 1 | 0.34 | 0.34 |
| TVS DIODE 9VWM 15.4VC SMA | Littelfuse Inc. | SMAJ9.0A | 2 | 0.36 | 0.72 |
| TVS DIODE 16VWM 26VC SMA | Littelfuse Inc. | SMAJ16A | 2 | 0.36 | 0.72 |
| CONN SMA JACK R/A 50OHM PCB | TE Connectivity AMP Connectors | 1470509-1 | 3 | 7.291 | 21.873 |
| FIXED IND 1.5UH 1.5A 120 MOHM | Abracon LLC | AIML-1206HC-1R5M-T | 11 | 0.46 | 5.06 |
| MOSFET N-CH 100V 730MA SOT89-3 | Microchip Technology | TN2510N8-G | 2 | 0.84 | 1.68 |
| RES SMD 4.7K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C4701FP500 | 2 | 0.0516 | 0.1032 |
| RES SMD 10K OHM 5% 1/10W 0603 | Vishay Beyschlag | MCT06030C1002FP500 | 4 | 0.0516 | 0.2064 |
| RES SMD 1K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C1001FP500 | 11 | 0.0516 | 0.5676 |
| RES SMD 100 OHM 1% 1/4W 1206 | Yageo | RC1206FR-07100RL | 1 | 0.013 | 0.013 |
| RES SMD 2.2M OHM 1% 1/4W 1206 | Vishay Dale | CRCW12062M20FKEA | 1 | 0.0548 | 0.0548 |
| RES SMD 1K OHM 0.1% 1/4W 1206 TC25ppm | Yageo | RT1206BRD071KL | 2 | 0.505 | 1.01 |
| RES SMD 10K OHM 0.1% 1/4W 1206 TC25ppm | Yageo | RT1206BRD0710KL | 1 | 0.505 | 0.505 |
| RES SMD 10 OHM 0.5% 1/8W 0805 | Yageo | RT0805DRE0710RL | 8 | 0.14 | 1.12 |
| RES SMD 470 OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C4700FP500 | 4 | 0.0516 | 0.2064 |
| RES SMD 20K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C2002FP500 | 4 | 0.0516 | 0.2064 |
| RES SMD 1K OHM 1% 1/4W 1206 | Yageo | RC1206FR-071KL | 2 | 0.013 | 0.026 |
| RES SMD 0.0OHM JUMPER 1/10W 0603 | Yageo | RC0603FR-070RL | 2 | 0.0053 | 0.0106 |
| RES SMD 49.9K OHM 1% 1/10W 0603 | Yageo | RC0603FR-0749K9L | 3 | 0.0057 | 0.0171 |
| RES SMD 620 OHM 0.1% 1/10W 0603 TC25ppm | Yageo | RT0603BRD07620RL | 2 | 0.2376 | 0.4752 |
| RES SMD 100K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C1003FP500 | 1 | 0.0516 | 0.0516 |
| RES SMD 2K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C2001FP500 | 2 | 0.0516 | 0.1032 |
| RES SMD 84.5KOHM 0.1% 1/10W 0603 TC25ppm | Yageo | RT0603BRD0784K5L | 1 | 0.2376 | 0.2376 |
| RES SMD 169K OHM 0.1% 1/10W 0603 TC25ppm | Panasonic Electronic Components | ERA-3AEB1693V | 1 | 0.63 | 0.63 |
| RES SMD 499 OHM 0.1% 1/10W 0603 TC25ppm | Yageo | RT0603BRD07499RL | 1 | 0.2376 | 0.2376 |
| RES SMD 976 OHM 0.1% 1/10W 0805 TC10ppm | TE Connectivity AMP Connectors | 1676469-2 | 2 | 0.85 | 1.7 |
| RES SMD 20 OHM 1% 1/4W 1206 | Yageo | RC1206FR-0720RL | 2 | 0.00792 | 0.01584 |
| RES SMD 10 OHM 1% 0.4W 1206 | Vishay Beyschlag | MCA12060C1009FP500 | 2 | 0.387 | 0.774 |
| RES SMD 10 OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C1009FP500 | 2 | 0.0774 | 0.1548 |
| Grand total, $USD | 699.02834 |
Module for off-market transformer
| Description | Vendor | Vendor P/N | QTY | Cost, $USD | Total |
|---|---|---|---|---|---|
| CAP CER 100nF 35V X7R 0603 | Taiyo Yuden | GMK107B7104KAHT | 23 | 0.184 | 4.232 |
| RES SMD 0.0OHM JUMPER 1/10W 0603 | Yageo | RC0603FR-070RL | 2 | 0.0053 | 0.0106 |
| RES SMD 100 OHM 1% 1/4W 1206 | Yageo | RC1206FR-07100RL | 1 | 0.013 | 0.013 |
| RES SMD 1K OHM 1% 1/4W 1206 | Yageo | RC1206FR-071KL | 1 | 0.013 | 0.013 |
| RES SMD 49.9K OHM 1% 1/10W 0603 | Yageo | RC0603FR-0749K9L | 3 | 0.0057 | 0.0171 |
| RES SMD 100K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C1003FP500 | 1 | 0.0516 | 0.0516 |
| RES SMD 2.2M OHM 1% 1/4W 1206 | Vishay Dale | CRCW12062M20FKEA | 1 | 0.0548 | 0.0548 |
| CAP CER 1800PF 50V NP0 0603 2% | Murata Electronics North America | GRM1885C1H182GA01D | 1 | 0.0836 | 0.0836 |
| RES SMD 4.7K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C4701FP500 | 2 | 0.0516 | 0.1032 |
| RES SMD 2K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C2001FP500 | 2 | 0.0516 | 0.1032 |
| CAP CER 4.7UF 10V X7R 1206 | Yageo | CC1206KKX7R6BB475 | 1 | 0.1116 | 0.1116 |
| RES SMD 10 OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C1009FP500 | 2 | 0.0774 | 0.1548 |
| RES SMD 10K OHM 5% 1/10W 0603 | Vishay Beyschlag | MCT06030C1002FP500 | 4 | 0.0516 | 0.2064 |
| RES SMD 470 OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C4700FP500 | 4 | 0.0516 | 0.2064 |
| RES SMD 20K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C2002FP500 | 4 | 0.0516 | 0.2064 |
| IC EEPROM 2KBIT 1MHZ 8SOIC | Atmel | AT24C02D-SSHM-T | 1 | 0.213 | 0.213 |
| RES SMD 84.5KOHM 0.1% 1/10W 0603 TC25ppm | Yageo | RT0603BRD0784K5L | 1 | 0.2376 | 0.2376 |
| RES SMD 499 OHM 0.1% 1/10W 0603 TC25ppm | Yageo | RT0603BRD07499RL | 1 | 0.2376 | 0.2376 |
| CAP CER 1500PF 630V C0G 1206 | TDK Corporation | CGA5H4C0G2J152J115AA | 1 | 0.28 | 0.28 |
| CAP CER 1500PF 630V C0G 1206 | TDK Corporation | CGA5H4C0G2J152J115AA | 1 | 0.28 | 0.28 |
| LED GREEN CLEAR 1206 SMD | Wurth Electronics Inc | 150120GS75000 | 1 | 0.34 | 0.34 |
| IC REGISTER BUS 8STAGE 16SOIC | NXP Semiconductors | 74HC4094D,653 | 1 | 0.387 | 0.387 |
| DIODE BRIDGE 800V 1.5A 4-SMD | Fairchild Semiconductor | DF08S | 1 | 0.425 | 0.425 |
| RES SMD 620 OHM 0.1% 1/10W 0603 TC25ppm | Yageo | RT0603BRD07620RL | 2 | 0.2376 | 0.4752 |
| RES SMD 10K OHM 0.1% 1/4W 1206 TC25ppm | Yageo | RT1206BRD0710KL | 1 | 0.505 | 0.505 |
| IC 4.55V SUPPLY MONITOR 8-SOIC | Texas Instruments | TL7705ACDR | 1 | 0.51 | 0.51 |
| RES SMD 1K OHM 1% 1/8W 0603 | Vishay Beyschlag | MCT06030C1001FP500 | 11 | 0.0516 | 0.5676 |
| RES SMD 169K OHM 0.1% 1/10W 0603 TC25ppm | Panasonic Electronic Components | ERA-3AEB1693V | 1 | 0.63 | 0.63 |
| TVS DIODE 9VWM 15.4VC SMA | Littelfuse Inc. | SMAJ9.0A | 2 | 0.36 | 0.72 |
| TVS DIODE 16VWM 26VC SMA | Littelfuse Inc. | SMAJ16A | 2 | 0.36 | 0.72 |
| RES SMD 10 OHM 1% 0.4W 1206 | Vishay Beyschlag | MCA12060C1009FP500 | 2 | 0.387 | 0.774 |
| CAP CER 1000PF 1KV NP0 1206 | Kemet | C1206C102JDGACTU | 1 | 0.871 | 0.871 |
| RES SMD 16.9K OHM 0.1% 1/4W 1206 TC25ppm | Panasonic Electronic Components | ERA-8AEB1692V | 1 | 0.94 | 0.94 |
| RES SMD 30K OHM 0.1% 1/4W 1206 | Panasonic Electronic Components | ERA-8AEB303V | 1 | 0.94 | 0.94 |
| CAP CER 47nF 50V NP0 1206 | Murata Electronics North America | GRM31M5C1H473FA01L | 1 | 1.01 | 1.01 |
| RES SMD 1K OHM 0.1% 1/4W 1206 TC25ppm | Yageo | RT1206BRD071KL | 2 | 0.505 | 1.01 |
| CAP CER 0.022UF 630V C0G 1210 | TDK Corporation | C3225C0G2J223J230AA | 1 | 1.025 | 1.025 |
| RES SMD 10 OHM 0.5% 1/8W 0805 | Yageo | RT0805DRE0710RL | 8 | 0.14 | 1.12 |
| CAP CER 0.47UF 50V X7R 0603 | TDK Corporation | C1608×7R1H474M080AE | 4 | 0.304 | 1.216 |
| CAP CER 2.2UF 50V X7R 1206 | Murata Electronics North America | GRJ31CR71H225KE11L | 4 | 0.318 | 1.272 |
| SW DIP EXT RCKR SEALED 8POS 30V | Grayhill Inc. | 76SB08ST | 1 | 1.441 | 1.441 |
| OPTOISOLTR 5KV 4CH TRANS 16-SMD | ON Semiconductor | PS2501L-4 | 1 | 1.734 | 1.734 |
| CAP CER 10UF 35V X7R 1206 | Taiyo Yuden | GMK316AB7106KL-TR | 4 | 0.49 | 1.96 |
| SENSOR TEMP RATIOMETRIC SOT23-6 | Maxim Integrated | MAX6610AUT+T | 1 | 2.117 | 2.117 |
| TERM BLK 3POS 5.08MM SPRING GRN | Phoenix Contact | 1790296 | 1 | 2.557 | 2.557 |
| CAP TANT 100UF 20V 10% 2917 | Vishay Sprague | TR3D107K020C0080 | 2 | 1.551 | 3.102 |
| FIXED IND 1.5UH 1.5A 120 MOHM | Abracon LLC | AIML-1206HC-1R5M-T | 11 | 0.46 | 5.06 |
| CONN HEADER 10POS .100 R/A SMD | Molex, LLC | 15912105 | 1 | 5.343 | 5.343 |
| CONN DIN RCPT 32POS DUAL RT ANG | Hirose Electric Co Ltd | PCN10C-32S-2.54DS(72) | 1 | 5.911 | 5.911 |
| IC REG PUSH-PULL ISO 1A 16TSSOP | Linear Technology | LT3439EFE#PBF | 1 | 7.04 | 7.04 |
| INDUCT ARRAY 2 COIL SMD | Eaton Bussmann | CTX02-13665 | 1 | 7.81 | 7.81 |
| IC OPAMP GP 8MHZ 8SO | Linear Technology | LT1007CS8#PBF | 2 | 4.15 | 8.3 |
| IC OPAMP GP 50MHZ 8SOIC | Analog Devices Inc. | AD847JRZ | 1 | 8.39 | 8.39 |
| IC REG LDO NEG ADJ 0.6A 10DFN | Linear Technology | LT3090EDD#PBF | 2 | 4.65 | 9.3 |
| IC REG LDO ADJ 0.2A 10DFN | Linear Technology | LT3042EDD#PBF | 2 | 4.9 | 9.8 |
| CONN SMA JACK R/A 50OHM PCB | TE Connectivity AMP Connectors | 1470509-1 | 3 | 7.291 | 21.873 |
| Grand total, $USD | 124.0117 |
Module assembly
Image A: Assembly in progress, front component side
Image A: Assembly in progress, back side, no parts here
Image A: Testing digital interface with Tektronix P6860 probe
Image A: Ultra-low noise Linear LDO’s assembly
Image A: Low noise Linear LDO’s assembly, hand soldering
%(imgref)Image A: Overview with both LDOs and Linear LT3439 Ultralow noise DC/DC Transformer Driver
Image A: Power testing and assembly mess
Image A: Special XICOR X24C01 ROMs, battery connector and off-shelf transformer
Module validation and debug
Preamp calibration
Per Keithley 1801 instruction manual for setup calibration we will need accurate DC source, low-thermal voltage divider, shorting strap and low-thermal 10K resistor.
Here’s setup I’ll use to calibrate EM A10 with Keithley 2001M using our preamp supply board:
| Manufacturer | Model | Description | Notes |
|---|---|---|---|
| HP | 3245A | DC source | Reference changed to LTZ1000ACH |
| DIY voltage divider | Measured ratios 100, 1000, 10000 | ||
| Keithley | 182M | Test nanovoltmeter | Used to measure divider output |
| HP | 3458A | Test DMM | Control meter |
| VPG | VHP | 10K foil resistor | 0.3ppm/K low-thermal |
| Foam box | Thermal isolation chamber |
Below is calibration procedure in steps:
STEP 1. Clean the input terminals, then connect the low thermal shorting strap to the EM A10 INPUTS terminals. I used copper single-strand from CAT5 Ethernet cable.
STEP 2. Put preamplifier module in the thermal isolation enclosure. Remove the lid only while making adjustments.
STEP 3. Turn on the Model 2001 power, and make sure the preamplifier is enabled. Select 20μV DC range, and allow a two-hour warm-up period before proceeding with the offset
adjustments.
STEP 4. Adjust the voltage offset control (V ZERO) for a Model 2001 front panel reading of 0μV ±0.001μV.
STEP 5. Enable the REL mode to null any remaining offset.
STEP 6. Disconnect the low-thermal shorting strap from the INPUTS terminals.
STEP 7. Connect the 10kΩ low thermal resistor to the INPUTS terminals, (For best results, remove the lead plating before use.)
STEP 8. Allow a 15 minutes warm-up period before proceeding with the current offset adjustments.
STEP 9. Adjust the current offset adjustments (I ZERO) for a Model 2001 front panel reading of 0μV ±0.1μV.
STEP 10. Disconnect resistor. Offset adjustments are complete, now we can start normal gain calibration.
Image A: Calibration setup
STEP 11. Connect DC calibrator/source to preamp using copper-copper wire
STEP 12. Set source to 0.00000 VDC, Divider ratio 100, allow 5 min warm-up. Execute :CAL:UNPR:PRE:Z1K GPIB command
STEP 13. Set source to 0.00000 VDC, Divider ratio 1000, allow 5 min warm-up. Execute :CAL:UNPR:PRE:Z10K GPIB command
STEP 14. Set source to 0.00000 VDC, Divider ratio 10000, allow 5 min warm-up. Execute :CAL:UNPR:PRE:Z100K GPIB command
STEP 15. Set source to 0.20000 VDC, Divider ratio 10000, allow 5 min warm-up. Measure ~20µV output with nanovoltmter. Execute :CAL:UNPR:PRE:FS100K Measured voltage value
STEP 16. Set source to 0.20000 VDC, Divider ratio 1000, allow 5 min warm-up. Measure ~200µV output with nanovoltmter. Execute :CAL:UNPR:PRE:FS10K Measured voltage value
STEP 17. Set source to 0.20000 VDC, Divider ratio 100, allow 5 min warm-up. Measure ~2mV output with nanovoltmter. Execute :CAL:UNPR:PRE:FS1K Measured voltage value
STEP 18. :CAL:UNPR:PRE:CALC
STEP 19. :CAL:UNPR:PRE:DATE ‘12/02/15’
STEP 20. :CAL:UNPR:PRE:NDUE ‘01/02/16’
STEP 21. :CAL:UNPR:PRE:SAVE
Now if calibration completed without errors, DMM should be ready to measure using preamp module, in our case EM A10 with our power supply card.
Experiment setup
Photo of test rig
Complete test rig consist of next components:
Keithley 2002 8½-digit DMM
Keithley 182 6½-digit nanovoltmeter
EM A10 nanovolt amplifier
AC coupling adapter
HP 3458A
Test results
And measurement using 20 µV range with copper shorted inputs on A10.
Total vertical scale is +1 to -1 nV and overall graph span is 120 minutes.
Conclusion
TBD
Credits for making this all possible come to Chuck from EEVBlog.com for all priceless contributions on this project!
Modified: May 6, 2024, 2:42 a.m.