Review and calibration of Advantest R6452A 5.5-digit DMM

Contents

Intro

The R6452A is digital multimeter equipped with dual input A/D converter path that allow independent measurement of two signals. These multimeters are targeted for lab/ATE measurement and device testing by configuring as versatile measurement system. The channel A has measurement functions including DCV/DCI, ACV/ACI, two-wire resistance and frequency, while the channel B has DCV/DCI and ACI. There is also input port at the rear for Type K thermocouple temperature measurements.

R6452A have RS-232 interface and optional GPIB interface card to use in automated systems. The remote command language is not compliant with SCPI but using own protocol, similar to one used in other Advantest and older Keithley/HP equipment with simple letter commands.

Today R6452A meters are long obsolete and replaced by newer ADCMT 7352A model which have slightly better specifications, modern USB interface, but follows same design concept and targeted market.

Key features:

  • Maximum display : 199999/199999 counts, 5½-digit resolution
  • Measurement function : DCV, ACV, DCI, ACI, 2w-resistance, low-power resistance, Frequency, Diode, Continuity (A channel), DCV,DCI,ACI (B channel)
  • Rear input: Thermocouple Type K temperature
  • Sampling rate: FAST: 80 SPS, MED: 10 SPS, SLOW: 2.5 SPS
  • Base range : 2 VDC
  • DC voltage measurement best accuracy: 180ppm + 5 digits, Resolution: 1 µV (Ach/Bch)
  • DC current measurement range : 200mA and 10A
  • AC voltage measurement: 20Hz to 100kHz, 200mV – 700V ranges
  • AC current measurement: 20Hz to 5kHz, 200mA and 10A ranges
  • Interface : RS232, optional GPIB
  • Form-factor : Half-width 19” 2U rack or benchtop


Image 1: Instrument front panel

Those input jacks that Advantest uses are super-fragile, and really one of the worst jacks on any instruments we ever used. Same poor jacks used in 8½-digit R6581 so it’s common for Advantest instruments. Red color fused current input jack accepts only maximum 200mA input, so be sure not to supply too much current, or you will have to find new 5mm 200mA glass fuse.

Buttons on the front panel are tiny, and some of the labels are rather cryptic, like SM or MD. Having no public manuals in English also does not help understanding meter operation.


Image 2: Instrument rear panel

This particular instrument came with GPIB option, but standard unit supplied only with RS232 interface. Banana jacks on the rear dedicated for thermocouple connections only. Unit have mains voltage selector block combined with protection mains fuse. All Advantest instruments are manufactured in Japan.

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Manuals and comparison to production standards

Design and construction

Removing two screws and pulling cover off reveals simple assembly and internal design.


Image 3: Cover removed, top view

Blue cables going across the instrument are from input jacks. Ribbon cable carry digital signals between out-guard CPU section and GPIB interface board. Advantest have also other options for integrating R6452A into automated test jigs and even optional battery +12V pack to provide standalone operation. There are not that many 5½-digit DMMs that can be powered from battery, which can be useful in field work.

As typical with many other benchtop DMMs, this one also based around Motorola RISC processor, Motorola MC68HC11A to be precise. There is also custom Advantest ASIC next to it, with label SIM-10272-152 doing glue logic and front panel communication. Socketed firmware ROM is TMS27C010A-10 in ceramic DIP package.


Image 4-5: Bottom side and input protection circuits

Other than little board mod diode, there are no components populated on the bottom side. One can find function switch relays and protection circuits near the input cable connections.


Image 6-7: Battery backup cell, front panel controller IC

RS232C level translation handled by Maxim MAX202CWE and UART controller Hitachi HD63B50P. Power regulator is located nearby, Linear LT1071CT. Date codes on IC suggest manufacturing date around 30th week of 1995. Battery help to retain SRAM contents with instrument readings and settings. Hopefully calibration data is stored in non-volatile memory, perhaps small SOIC-8 chip with 953B marking?


Image 8-9: FPC cable for front panel, firmware ROM chip

High-voltage DC/DC converter located on small daughter board right on the front panel PCB. This is required to generate proper levels for VFD screen operation.


Image 10-11: GPIB interface card

GPIB card using industry standard TMS9914 controller, some digital logic latches and 75160/75161 GPIB drivers. Small Lattice PAL/GAL device handle interrupts and dataflow.

Analog front-end section

Time to remove aluminum shield from analog section and study overall design.


Image 12: ADC ASIC and key features

ADC and control of the analog functions is implemented by custom Advantest ASIC, with label SIA-87841. There are lot of Linear LTC1050 chopper opamps around as well. Green epoxy resistor networks maintain accurate and stable ratios between various signals. One of these resistors used as high-voltage divider for 200V and 1kV ranges.

A/D converter input range is +/-2V. As result input resistance >1 GΩ is provided only for 200mV and 2V ranges, while higher ranges are using 10 MΩ input divider.


Image 13-14: LT1027 5V main reference


Image 15-16: TrueRMS converter circuit

AC RMS conversion is handled by widely known chip for the purpose, AD637. Same chip we can find in other benchtop meters, even high-performance type such as Keithley 2001 and Keithley 2002.


Image 17-18: Input terminals connections and current shunts

10A current input protected by high-quality HRC 15A Littelfuse fuse, placed on the socket for easy service. 0.1 Ω shunt is standing right next to the fuse, with smaller 1 Ω SMT-type shunt located under it. There are no low current ranges on this DMM, so current measurement function is rather simple.


Image 19-20: Isolation barrier

Interfacing between floating analog domain section and earth-referenced digital outguard section done thru four PC817 optocouplers. This means that communication between the processor and analog chipset is done serially thru some kind of SPI or UART-alike interface.


Image 21-22: Power transformers

Power is provided thru isolation transformer TP-348-DC-T. Mains transformer bears similar marking, with AC-T ending. Both transformers are unique to Advantest and custom made for this DMM.


Image 25-26: Film resistive networks


Image 23-24: Bottom side of the analog section, shields removed

There are no components on the back of the PCBA.

Thermocouple rear input assembly


Image 27-28: Thermocouple input PCBA

Thermocouple input at the rear using own PCBA, interconnected thru DIN-type connector with mainboard. Input terminals have proper thermocouple cold-junction compensator LT1025, that provide 0.5 °C initial accuracy for correct Type K probe measurements. There are four more LTC1050 chopper opamps, large black epoxy resistor network and few analog 4052/4053 switches to route signal for ADC.

NAIS AQW614A PhotoMOS provide signal protection for the sensitive inputs.

Firmware

Firmware ROM dumps from single TMS27C010A ROM, read by general purpose ROM programmer.

Firmware version Binary file Checksum
Model R6452A A04, SIS-003731, U52 ROM Binary file CHK:0×0018A8A5F

Calibration testing

To test performance and perform calibration we will utilize what is available in lab:

  • Fluke 5720A for DCV, ACV, DCI, ACI and Resistance tests. Calibrated February 10, 2019
  • Fluke 5720A + 5725A amplifier for 10A DCI and ACI tests. Calibrated February 10, 2019
  • Keysight 3458A as reference standard for calibration verification
  • Wavetek 4920M as reference meter for calibration verification
  • Set of shielded Fluke 5440A-7002 cables with copper low-thermal dual banana connectors


Image 29: R6452A during calibration, showing connections to Fluke 5720A

Calibrator was artifact calibrated to reference standards just a 19 days ago, but at accuracy levels of R6452A that is completely unnecessary. Even annual specifications of Fluke 5720A provide good TUR to meet all specifications of this DMM so the calibrator tested just to provide good confidence in results. Ambient temperature was kept at +23 °C ±1 °C.

No adjustments were performed for this DMM and the original calibration date/time is unknown.

Test point Measured value Source uncertainty, ppm DUT spec, ppm Deviation Result, %/spec TUR
-19 mV -0.018987 25.05 496 ppm -684 ppm 138.0% 5.4
-10 mV -0.010002 44.00 780 ppm 200 ppm 25.6% 9.5
+10 mV 0.009991 44.00 780 ppm -900 ppm 115.4% 17.7
+19 mV 0.018988 25.05 496 ppm -632 ppm 127.4% 19.8
-190 mV -0.18997 6.11 212 ppm -158 ppm 74.6% 34.7
-100 mV -0.10000 8.00 240 ppm 0 ppm 0.0% 30.0
+100 mV 0.09993 8.00 240 ppm -700 ppm 291.7% 30.0
+190 mV 0.18990 6.11 212 ppm -526 ppm 248.8% 34.7
-1.9 V -1.8996 3.37 206 ppm -211 ppm 102.0% 61.3
-1.0 V -1.0000 3.70 230 ppm 0 ppm 0.0% 62.2
+1.0 V 0.9993 3.70 230 ppm -700 ppm 304.3% 62.2
+1.9 V 1.8990 3.37 206 ppm -526 ppm 255.1% 61.3
-19 V -18.997 2.21 206 ppm -158 ppm 76.5% 93.3
-10 V -10.000 2.25 230 ppm 0 ppm 0.0% 102.2
+10 V 9.9963 2.25 230 ppm -370 ppm 160.9% 102.2
+19 V 18.990 2.21 206 ppm -526 ppm 255.1% 93.3
-190 V -189.98 3.21 206 ppm -105 ppm 51.0% 64.3
-100 V -100.01 3.40 230 ppm 100 ppm 43.5% 67.6
+100 V 99.93 3.40 230 ppm -700 ppm 304.3% 67.6
+190 V 189.89 3.21 206 ppm -579 ppm 280.6% 64.3
-500 V -499.88 4.80 280 ppm -240 ppm 85.7% 58.3
-1000 V -999.73 4.40 230 ppm -270 ppm 117.4% 52.3
+1000 V 999.63 4.40 230 ppm -370 ppm 160.9% 52.3
+500 V 499.79 4.80 280 ppm -420 ppm 150.0% 58.3

From DC Voltage test results meter is unable to meet it’s specifications and need to be adjusted.

Test point Measured value Source uncertainty, ppm DUT spec, ppm Deviation Result, %/spec TUR
10.000322 Ω 9.99000 23 1000 -1032 ppm -103.2% 43.5
19.000006 Ω 18.996 23 716 -211 ppm -29.5% 31.1
100.00319 Ω 100.013 10 460 98 ppm 21.3% 46.0
189.99882 Ω 189.932 10 432 -352 ppm -81.5% 43.2
1000.0099 Ω 999.78 8 250 -230 ppm -92.0% 31.2
1900.0239 Ω 1899.52 8 226 -265 ppm -117.2% 28.3
9999.786 Ω 9998.9 8 250 -89 ppm -35.4% 31.3
18999.392 Ω 18997.6 9 226 -94 ppm -41.7% 25.1
99994.64 Ω 99980 9 250 -146 ppm -58.6% 27.8
189988.81 Ω 189962 9 226 -141 ppm -62.4% 25.1
999980.6 Ω 999660 16 360 -321 ppm -89.1% 22.5
1899967 Ω 1899860 17 332 -56 ppm -17.0% 19.5
9999029 Ω 9995400 33 2100 -363 ppm -17.3% 63.6
18998410 Ω 18991200 43 2053 -380 ppm -18.5% 47.7
100007070 Ω 99960000 100 20000 -471 ppm -2.4% 200.0

Resistance results are not as bad as DC Voltage, however 2KΩ range could use some adjustment help.

Test point Measured value Source uncertainty, ppm DUT spec, ppm Deviation Result, %/spec TUR
-19 mA -0.019001 39.2 1316 53 ppm 4.0% 33.6
-10 mA -0.010003 43.0 1600 300 ppm 18.7% 37.2
+10 mA 0.009990 43.0 1600 -1000 ppm -62.5% 37.2
+19 mA 0.018989 39.2 1316 -579 ppm -44.0% 33.6
-190 mA -0.189951 53.0 1032 -258 ppm -25.0% 19.5
-100 mA -0.099975 49.2 1060 -250 ppm -23.6% 21.5
+100 mA 0.099967 49.2 1060 -330 ppm -31.1% 21.5
+190 mA 0.189938 53.0 1032 -326 ppm -31.6% 19.5
-1.9 A -1.8992 73.1 1316 -421 ppm -32.0% 18.0
-1.0 A -1.0000 85.0 1600 0 ppm 0.0% 18.8
+1.0 A 0.9986 85.0 1600 -1400 ppm -87.5% 18.8
+1.9 A 1.8981 73.1 1316 -1000 ppm -76.0% 18.0
-5 A -4.9977 372.7 1120 -460 ppm -41.1% 3.0
-10 A -9.9972 372.7 1060 -280 ppm -26.4% 2.8
+10 A 9.9962 372.7 1060 -380 ppm -35.8% 2.8
+5 A 4.9979 372.7 1120 -420 ppm -37.5% 3.0

To our surprise, DC current function is still in spec, even when measuring current at mere 5% of the scale!

Test point Measured value Source uncertainty, ppm DUT spec, ppm Deviation Result, %/spec TUR
10 mV, 20 Hz 0.010028 312.27 41000 2800 ppm 6.8% 131.3
10 mV, 1 kHz 0.010062 312.27 22000 6200 ppm 28.2% 70.5
100 mV, 20 Hz 0.099360 121.36 9500 -6400 ppm -67.4% 78.3
100 mV, 1 kHz 0.099785 121.36 4000 -2150 ppm -53.8% 33.0
190 mV, 20 Hz 0.189110 121.36 7842 -4684 ppm -59.7% 64.6
190 mV, 1 kHz 0.189916 121.36 3053 -442 ppm -14.5% 25.2
190 mV, 10 kHz 0.189955 121.36 3053 -237 ppm -7.8% 25.2
190 mV, 20 kHz 0.189843 121.36 3053 -826 ppm -27.1% 25.2
190 mV, 100 kHz 0.186016 590.91 42632 -20968 ppm -49.2% 72.1
1.0 V, 20 Hz 0.99390 49.55 9500 -6100 ppm -64.2% 191.7
1.0 V, 60 Hz 0.99758 49.55 4000 -2420 ppm -60.5% 80.7
1.0 V, 1 kHz 0.99786 49.55 4000 -2140 ppm -53.5% 80.7
1.0 V, 10 kHz 0.99808 49.55 4000 -1920 ppm -48.0% 80.7
1.0 V, 20 kHz 0.99855 49.55 4000 -1450 ppm -36.2% 80.7
1.0 V, 100 kHz 1.0146 138.18 45000 14600 ppm 32.4% 325.7
1.9 V, 20 Hz 1.8917 49.55 7842 -4368 ppm -55.7% 158.3
1.9 V, 45 Hz 1.8977 49.55 7842 -1211 ppm -15.4% 158.3
1.9 V, 1 kHz 1.89932 49.55 3053 -358 ppm -11.7% 61.6
1.9 V, 10 kHz 1.89986 49.55 3053 -74 ppm -2.4% 61.6
1.9 V, 20 kHz 1.90082 49.55 3053 432 ppm 14.1% 61.6
1.9 V, 100 kHz 1.93305 138.18 42632 17395 ppm 40.8% 308.5
10.0 V, 20 Hz 9.9482 48.18 9500 -5180 ppm -54.5% 197.2
10.0 V, 60 Hz 9.9825 48.18 4000 -1750 ppm -43.8% 83.0
10.0 V, 1 kHz 9.987 48.18 4000 -1300 ppm -32.5% 83.0
10.0 V, 10 kHz 9.9875 48.18 4000 -1250 ppm -31.2% 83.0
10.0 V, 20 kHz 9.9865 48.18 4000 -1350 ppm -33.8% 83.0
10.0 V, 100 kHz 9.9667 121.36 45000 -3330 ppm -7.4% 370.8
19 V, 60 Hz 18.9815 48.18 3053 -974 ppm -31.9% 63.4
19 V, 1 kHz 18.9905 48.18 3053 -500 ppm -16.4% 63.4
19 V, 10 kHz 18.9915 48.18 3053 -447 ppm -14.7% 63.4
19 V, 20 kHz 18.9912 48.18 42632 -463 ppm -1.1% 884.8
19 V, 100 kHz 18.971 121.36 3053 -1526 ppm -50.0% 25.2
100 V, 60 Hz 99.891 60.18 4000 -1090 ppm -27.2% 66.5
100 V, 1 kHz 99.942 60.18 4000 -580 ppm -14.5% 66.5
100 V, 10 kHz 99.943 60.18 4000 -570 ppm -14.3% 66.5
100 V, 20 kHz 99.936 60.18 4000 -640 ppm -16.0% 66.5
100 V, 100 kHz 99.539 173.64 45000 -4610 ppm -10.2% 259.2
190 V, 60 Hz 189.817 60.18 3053 -963 ppm -31.6% 50.7
190 V, 1 kHz 189.910 60.18 3053 -474 ppm -15.5% 50.7
190 V, 10 kHz 189.911 60.18 3053 -468 ppm -15.3% 50.7
190 V, 20 kHz 189.900 60.18 3053 -526 ppm -17.2% 50.7
190 V, 100 kHz 189.312 173.64 42632 -3621 ppm -8.5% 245.5
300 V, 60 Hz 299.690 78.64 8667 -1033 ppm -11.9% 110.2
300 V, 1 kHz 299.790 78.64 8667 -700 ppm -8.1% 110.2
300 V, 10 kHz 299.800 78.64 8667 -667 ppm -7.7% 110.2
700 V, 60 Hz 699.270 78.64 4857 -1043 ppm -21.5% 61.8
700 V, 1 kHz 699.590 78.64 4857 -586 ppm -12.1% 61.8

AC Voltage is also okay, meeting specs with decent margin on most of the points.

Test point Measured value Source uncertainty, ppm DUT spec, ppm Deviation Result, %/spec TUR
19 mA, 60 Hz 0.018971 138.18 16526 -1526 ppm -9.2% 119.6
19 mA, 1 kHz 0.018988 138.18 60526 -632 ppm -1.0% 438.0
100 mA, 60 Hz 0.099745 133.64 8000 -2550 ppm -31.9% 59.9
100 mA, 1 kHz 0.099823 133.64 52000 -1770 ppm -3.4% 389.1
100 mA, 5 kHz 0.099874 133.64 8000 -1260 ppm -15.8% 59.9
190 mA, 1 kHz 0.189925 133.64 51053 -395 ppm -0.8% 382.0
1.0 A, 60 Hz 0.996600 308.18 26000 -3400 ppm -13.1% 84.4
1.0 A, 1 kHz 0.999000 308.18 70000 -1000 ppm -1.4% 227.1
1.9 A, 60 Hz 1.884500 308.18 16526 -8158 ppm -49.4% 53.6
1.9 A, 1 kHz 1.888400 308.18 60526 -6105 ppm -10.1% 196.4
10 A, 60 Hz 9.972500 385.45 8000 -2750 ppm -34.4% 20.8
10 A, 1 kHz 9.995200 385.45 52000 -480 ppm -0.9% 134.9

AC Current show no problems either.

DCV linearity verification


Image 30: R6452A 20VDC range linearity test, using -11 to +11V DC

There is no linearity specification in the datasheet, so we can assume this spec to be ±25 ppm based on the counts error specified for the range. Ideally we should have tested 2V range, but since typical precision application commonly used 10V, tested was performed using -11.0 to +11.0 sweep. Keysight 3458A INL is essentially invisible zero on the scale of R6452A DMM.

Summary

Stay tuned and let us know your feedback! Discussion about this article and related stuff is welcome in comment section or at our own IRC chat server: irc.xdevs.com (standard port 6667, channel: #xDevs.com). Web-interface for access mirrored on this page.

Author: Illya T.
Published: March 2, 2019, 8:05 p.m.
Modified: March 3, 2019, 5:47 p.m.

References

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