My measurement devices

Dual slope integration: (Control unit, counter, integrator, source of Vref).
- Input: Vin. Linear growth by integration Vo → Vx for digital counted fixed time t1.
- Input: switch Vin → Vref.
- Input: Vref. Linear fall by integration down Vx → Vo for time t2, measured by counting.   Vin = Vref * t2 / t1.

Nice design:  Micronta 22-167.
Another beauties: chocolate,   pudding.
Actually used:  Soar 4030B, another gray Soars.
How it works:
Measurements of resistance, capacitance, frequency, current, voltage and rectification, auto power off in KT9901, KT9902 multimeters.
Some simple digital multimeters and their solutions for decimal point displaying.

Voltcraft VC920
Bought: May 2013 at Voelkner.

Voltcraft VC 920 calibrated
9V(block), 8mA. For measuring voltage, current both DC/AC, resistance, capacity, frequency till 400 MHz, temperature.
Works with 2 switchable accuracies. At 4V measuring range the better accuracy is ± 0.08 % + 10 dgt.
The accuracy is hold for temperature 23°C±5°C and rel. humidity less then 75%.
What does it mean, if I measure an 1.5 AA battery element and read from display 1.4074 V ?

0.08% from 1.4074 is aproximatelly 0.00113. The measured value is therefore between 1.40627 and 1.40853 V.
Last 10 digits place the displayd value from 1.4064 V till 1.4084 V.

If we take in account both, then the measured value is 1.407 V ± 0.002 V.
For orientation by the next measured values, if we take 1407 mV as reference value, then ±1 % is ±0.014 - from 1.393 V to 1.421 V.

Voltcraft VC140
9V(block). Lowcost multimeter.
Measured element: 1.397 V (-0.010).

Norma Normameter MP12
9V(block), < 1mA. Norma MCC1 or MCC2(ADC,...), NEC D7514G(CPU with dsp,kbd interf.), AD636JH(RMS→DC), TLC271, 93C46PC(EEPROM).
Probably same as Siemens B1021.
Measured element: 1.407 V (+0.000).

Norma Normameter MP13
9V(block), < 1mA. Norma custom IC MCC2(ADC,...), NEC D7514G(CPU with dsp,kbd interf.), AD636JH(RMS→DC), TLC372CP(comp), 93C46PC(EEPROM), 2*271C(OA), HEF4104(volt.transl.).
Measured element: 1.408 V (+0.001).

Norma Normameter MP14
9V(block), < 1mA. custom IC Norma MCC2(ADC,...), NEC D7514G(CPU with dsp,kbd interf.), AD636JH(RMS→DC), TLC372CP(comp), 93C46PC(EEPROM), 2*271C(OA), HEF4104(volt.transl.).
Probably same as Siemens B1022 and Gossen MAVO40.
Measured element: 1.433 V (+0.026).

Norma Normameter MP11
9V(block), custom IC Norma MCC1 or MCC2(ADC,...), NEC D7514G(CPU with dsp,kbd interf.), 93C46PC(EEPROM), 2*271C(OA).
Probably same as Siemens B1020.

Siemens B1022
9V(block), 1mA. Custom IC Norma MCC1, NEC D7514G.

Probably same as Norma MP13 or Gossen MAVO30.

7KB 9102-8CA: Surface-plunger-feeler up to 600°C.
Measured element: 1.406 V (-0.001).

Hartig & Helling VM-100D
9V(block), 1.5mA. For measuring V, 10A DC/AC, Ohm.
VR3 has no impact, VR under display adjusts V and also I measuring. V adjusted, I at 150mA gives 0.160A.
Measured element: 1.408 V (+0.001).

BY 1933A
9V(block). For measuring V, mA DC/AC, 10A, Ohm, diode test, transistor test.
Measured element: 1.409 V (+0.002).

Peertronic ADM-10B
3V(2*AA). Measures V, mA DC/AC, 10A, Ohm, diode test.
Measured element: 1.417 V (+0.010).

Pancontrol_KT-25
9V(block), 1.5V button for clock.
V, mA DC/AC, 20A, Ω, Capacitance, diode test. IC: ICL7106
. Measured element: 1.402 V (-0.005).

Monacor DMT-4500
9V(block), 1.1 mA.
IC: CIC806E(ICL7126), 3 x LM358, JRC062D, 2 x 4030 (4 x excl.OR).
Made in Taiwan 1987.
Measured element: 1.395 V (-0.012).

MIC-7S
9V(block), 0.4mA. IC: ICL7136. Made in Taiwan.
Measured element: 1.388 V (-0.019).

TEL DM1000B
9V(block), 0.2mA. IC: ICL7136.
Measured element: 1.436 V (+0.029).

Keithley 130
9V(block). V, mA DC/AC, 10A, Ω, input imp. 10 Mω.
Measured element: 1.407 V (+0.000).

Keithley 136
9V(block), 6mA. V, mA DC/AC, 10A, Ω, input resistance on 200 mV and 2V > 1000 MΩ, else 10 MΩ.
Measured element: 1.408 V (+0.001).

Fluke 21
9V(block), 0.3mA. Made in USA.
Measured element: 1.407 V (+0.000).

Beckman Circuitmate DM25
9V(block), 3.5mA.
IC: 7106,
LM358 (Dual opAmp), 4070(Quad Exclusive-OR Gate),...
Beckman Industrial Corporation.
A Subsidiary of Emerson Electric Co. Brea, CA, 92621, Made in Taiwan. Prod.year ~1983.
Measured element: 1.405 V (-0.002).

Beckman Industrial DM25 XL
9V(block), 0.2mA.
IC: 7106,
4*TL062(low power dual J-FET OA), 4521(24-stage frequency divider and oscillator),...
Beckman Industrial Corporation.
An Affiliate of Emerson Electric Co. Instrumentation Products Division San Diego, California.
Made in Taiwan.
Measured element: 1.409 V (+0.002).

Beckman Circuitmate DM25L
9V(block), 2.2mA.
AD IC: 7106. Basic DC accuracy: 0.8%.
Beckman Industrial Corporation.
Made in Taiwan. Prod.year 1985.
Measured element: 1.406 V (-0.001).

Micronta 22-167    Product of Radio Shack
3V (2*AA), 0.6mA. Auto power off.
Measured element: 1.407 V (+0.0) after adjusting with VR1.

Soar ME-550
3V(2*AA), 1 mA. IC:M5230. No manual range setting.
Measured element: 1.413 V (+0.006).

Soar 3430
9V(block), 7mA. Plug for external power supply.
Measured element: 1.411 V (+0.004).

Soar 3520
3V(2*AA), <1 mA, IC: M5230. Smaller device, no manual range setting.
Measured element: 1.408 V (+0.001).

Soar 4041A
3V(2*AAA), <1mA (2mW), DC V accuracy 0.3% + 1d. Display: digital: 2.3/s, analog bargraph: 23/s.
from booklet 1, from booklet 2.
Measured element: 1.407 V (-0.000).

Soar 4030B
3V(2*AAA), <1mA (2mW), DC V accuracy 0.3% + 1d. After 1 hour auto power off to 0.4mW. Booklet printed in 1989. Display: digital: 2.3/s, analog bargraph: 23/s.
Measured element: 1.407 V (-0.000).

Soar 4050B
3V(2*AAA), <1mA (2mW), DC V accuracy 0.1% + 1d. Freq. meas: 5Hz-100kHz. Display: digital: 2.3/s, analog bargraph: 23/s.
Measured element: 1.407 V (-0.000).

Soar 3255    sent to Anton T.(BG-D)
3V(2*AAA), 1 mA. IC: M6306.
Same or similar as Yokogawa 7534-03 and Hewlett Packard E2378A.
Measured element: 1.407 V (-0.000).

Soar 4055
3V(2*AAA), <1mA. IC: M6266. Same as SOAR 4050B, but rugged, waterproof.
Measured element: 1.406 V (-0.001).

ISHII DM 3350 Instrument Works Ltd, Yamanashi.
3V(2*AA), 1mA.
Measured element: 1.396 V (-0.011).

ISHII DM 4351 Instrument Works Ltd, Yamanashi.
3V(2*AA), 1mA, same device is Hioki 3216.
Measured element: 1.409 V (+0.002).

Hioki 3216
3V(2*AA), 1mA, same device is Ishii Instrument Works DM 4351.
Measured element: 1.407 V (+0.000).

Hioki 3230
9V(block), 3mA. Prod.year 1985.
Measured element: 1.405 V (-0.002).

Hioki 3231
3V(2*AA), 1mA. Prod.year 1988.
Measured element: 1.415 V (+0.008).

Sinometer DT9907C
9V(block), 6mA.
Measured element: 1.418 V (+0.011).

Metex M-4650CR    sent to Salvatore S.(IT)
9V(block), 5mA.
Measured element: 1.409 V (+0.002).

Metex M80
9V(block), 2mA. IC: 7149.
Same device: Voltcraft M80.
Measured element: 1.405 V (-0.002).

Chauvin & Arnoux C.A 5220 G    sent to Franziska K.(DE)
3V(2*AA). V-A-Ω-Hz-n/µF multimeter, input impedance 10MΩ or 270kΩ,
frequency only till 200kHz, capacitance 1pF-40µF, 3V-2*AA.
Measured element: 1.408 V (+0.001).

Metrix MX 44    sent to Detlef S.(DE)
9V, cca 1mA. V-A-Ω, capacity multimeter. DC V accuracy 0.3% + 1d. Auto power off after cca 30 min.
Measured element: 1.407 V (+0.000).

Hewlett Packard E2378A    sent to Metama UG.(DE)
3V(2*AAA), 1 mA. IC: M6306. The same, but not rugged case E2377A.
Same or similar Yokogawa 7534-03 and Soar 3255.
Measured element: 1.406 V (-0.001).

Beha 93-3000
9V(block), 1 mA. IC: TC818ACBQ.
Current range and voltage dividers resistors accuracy: 0.25%.
Measured element: 1.406 V (-0.001).

Düwi 07977
9V(block), 5mA.
IC: 7106, 2*opamp 2904D, 2*JFETopamp 062D and 2 other ICs.
Measured element: 1.404 V (-0.003).

KT-7032
9V(block), 2mA. Digital-analog, input imp. 10 MΩ, V,A-DC/AC, Ω, nF,µF.
Battery test: 1.5V with 15Ω ca 100mA; 9V with 900Ω ca 10mA.
KTI - Founded in 1996, Ketai Instrument (Kunshan) Co., Ltd. in China.
Measured element: 1.409 V (+0.002).

DMT 7000 Monacor ?
9V(block), <3 mA.
IC: CIC5136,      3*14070: quad XOR,   4*LM358: 2 of them only for Capacity meas.
741: with 1 LM358 only for 200Ω scope - zero adjust,
TC4528: dual monost.multivibrator + 4011: quad NAND - both only for frequency measurement.
Measured element: 1.423 V (+0.016), setting the trimmer 1.407 V (+0.000)

After adjusting the trimmer (at the picture in red circle) also at the 20V scope the accuracy was 1%. At 200mA current, resistance and capacitance scopes the accuracy was about 1%. For capacitance there is also a trimmer (at the picture in green circle). For both frequency scopes there are 2 trimmers (at the picture in blue circle). These scopes were not tested. Also the AC scopes were not tested.

In this device there is a 741 for zero adjusting on the 200Ω scale. (Also in KT9901 and KT9902). But here is a half of LM358 placed before 741. By all these OAs is the "-" input directly connected to output. (voltage followers). This LM358, where the second half of the OA is umused was defect. Also by KT9901 and KT9902 the 741 was defect. My suspicion is, that this directly connected "-" to output caused these defects.

KT 8801 Two color mutations.
Made in Taiwan 1989.   9V(block), 2mA.
IC: CIC5106,
4011:quad NAND, 4*14070:quad XOR, 14528: dual monost.multivibrator, JRC 062D, 3*LM358.

Measured element: 1.415 V (+0.008).

KT-65
9V(block), 7mA. IC: UM7106
Made in Taiwan 1992.
Measured element: 1.422 V (+0.015).

How it works

KT 9901










9V(block), 5mA. U, I, R with continuity check, C, diode, tr.hfe, auto power off.
Made in Taiwan 1993.   Measured element: 1.409 V (+0.002).


IC: UM7106R (R: 7106 with left-right reversed !),
uA741: setting "0" at 200 Ω range,
1/2 062D as comparator for beeper, 1/2 062D AC to DC converter for U, I, C measurements,
2*LM358 for measuring C,
MC14060 for auto power off.
The accuracy of divider resistors is 0.5% (green strip).

KT 9902












9V(block), 5mA, U, I, R with continuity check, frequency until 2 MHz, temperature, diode, tr.hfe, auto power off.
Made in Taiwan 1992.   Measured element: 1.411 V (+0.004).

IC: UM7106R (R: 7106 with left-right reversed !),
uA741 setting "0" at 200 Ω range,
1/2 062D as comparator for beeper, 1/2 062D AC to DC converter for U, I, C measurements,
7555 - CMOS timer 555 with improved performance as frequency to voltage converter,
TC4049 - inverting hex buffer/converter as input signal amplifier for frequency measurement,
HEF4518 - dual BCD counter as divider by 10 and 100 for frequency measurement,
MC14060 for auto power off.

83X multimeters based on IC 7106

DT-830B and DT-832
9V(block), 0.7 mA resp. 1.8 mA, input imp. 10 MΩ, V,A-DC, V-AC only 200 and 750V, Ω, trans.hFE.
Accuracy at V DC: ±0.5 %, ± 2 digits.
DT-832 has also continuity test buzzer and 50Hz square output.
Measured element DT-832: 1.402 V (-0.005).

Main divider at DT-832: 0.01(10A), 0.99, 9 and 100, 900, 9k, 90k, 358k+542k = 900k.

DT-830B: all divider resistors 0.25%, last two resistors 342+547=989k.
DT-832: all divider resistors with 0.25% accuracy, but last two resistors 0.5%.

Decimal points at DT-830B model:
I don't see any transistors, which should be used to invert the BP signal for showing the decimal point.
It works with an RC member M62;20n, which integrates the BP square signal. The scope traces are against COM.




Decimal points and HV displaying for 1000V DC and 750V AC at DT-832 model:
Battery V+ or ca 2.7V DC against COM for DP20, DP200 dec. points and HV indication.
It's the simplest way for displaying decimal points.




Another 830B concept:
Accuracy: Range setting resistors in this device have 0.5% accuracy.
Meausrement and range switching and decimal points with phase inverting NPN transistors S9014.
Blue track - BP against COM, yellow track - collector of DP200 phase inverting transistor.
1. decimal point displayed (reversed phase),
2. decimal point not displayed (in phase).

DMM3800-18
9V(block), IC: 7106 ?, HD4011BP, HD14070BP, JRC 062D.
Divider resistors accuracy: green strip 0.5%.
Measured element: no valid, parts of PCB burned out.

DT9205A
9V(block), 3 mA, IC: 7106 ?, 2 x LM324.
Divider resistors accuracy: brown strip 1%.
Measured element: 1.429 V (+0.022).

Wavetek DM78     seems to be same as Beckman Circuitmate DM78.
2 x 1,5V LR44 button.
Measurig only voltage DC/AC, ohms with buzzer and diode. Hard to open for battery change.
Measured element: 1.407 V (+0.0).

Mc Voice M-8SL
9V, 6mA.
Measurig voltage DC/AC, currents, ohms with buzzer, capacitors, diods and transistors.
Similar device: Mastech MS8207 and MS8208.


Voltage: DC: 400mV-400V: ±0.5%, 1000V: ±0.8%, AC: 4V-400V: ±0.8%
Current: DC: 4mA-40mA: ±0.8%, 400mA: ±1,5%, 10A: ±2.0%, AC: 4mA-400mA: ±1.5%
Resistance: 400Ω-4MΩ: ±0.8%, 40MΩ: ±1.0%
Frequency: 40kHz: ±1.5%
Capacitance: 40nF-40µF: ±4.0%
Measured element: 1.413 V (+0.006).

DM620 multimeter - data logger
Produced by: SMTech, Korea.
An interesting device.




3.7V(Li-ion 1400 mAh), 30mA. Loading current: 100mA. Basic accuracy: 0.05%
Mini USB, loading from 5V source or from PC-USB. PC-soft for controlling and data transfer.
IC's: D78FQ546, FS9704B-GC.


Functions: DCV, ACV, Ohm, Beep, Diode, Cap, DCmA, DCA, ACmA, ACA, Freq, Per, Duty, Temp (with K-type sens).
Menu: Data Logger, Record mode, Relative mode, Compare mode, Trend plot.

By Trend plot we can set REF voltage - mid value on V axis, H/DIV - horizontal step and V/DIV - vertical step.
Trend plot for DCV measure is limited - REF voltage and V/DIV to max 4.9999 V.
H/DIV is settable by steps between 20s and 10h.

Measured element: 1.407 V (+0.000).

Prova 903     TES Electrical Electronic Corp.
Two channels. 9V, 6-7 mA.
Measurig voltage DC/AC, current DC/AC, ohms with buzzer, capacitnce, diode.
Measured element: 1.413 V (+0.006).
sent to x(nasty) ↓