Electrical Test & Measurement · Digital Multimeters
Benchtop digital multimeter range in 4½, 5½ and 6½ digit models, with dual VFD or colour LCD displays, DCV to 1000 V, four-wire resistance and USB, GPIB or RS232 control.
TH1941 (6 models) ·
A bench multimeter earns its place by being the instrument the other instruments are checked against, or by being the one that runs unattended for a week. Those are different requirements, and this range separates them by resolution rather than by features.
Seven codes across three grades. The four-and-a-half digit models are the production instruments: fast, simple, with a dual display that shows two quantities at once. The five-and-a-half digit models add resolution, four-wire resistance and, on one model, a colour display. The six-and-a-half digit model is the reference instrument, with graphical views and the tighter resolution that a calibration bench needs.
All of them share a bench body with a front input panel, a mains inlet and a communication port at the rear. The VFD models carry a green dual display; the colour models carry a single LCD with a menu that can be set to English.
The functions are the ones a bench actually uses: voltage and current in both forms, resistance in two and four wire, frequency and period, continuity and diode. Maths functions - percent, dB, dBm and a relative offset - sit on the same keys.
The input is ranged, amplified and then digitised by an integrating converter. Integration is what rejects mains hum: the conversion window is chosen so that a whole number of mains cycles falls inside it, and the interference averages to zero rather than being sampled into the result.
Alternating quantities pass through a true-RMS converter, which squares the signal, averages it and takes the square root. That is why the reading follows the heating effect of a distorted waveform rather than the average of its half-cycles, and why the stated bandwidth matters: outside it the converter no longer follows the input.
Resistance is measured by forcing a known current and reading the resulting voltage. In two-wire mode the same leads carry both, so their resistance is included. In four-wire mode a separate sense pair taps the voltage directly at the component, and the lead resistance drops out of the result - which is the only way a low-value resistor can be measured meaningfully on a bench.
The comparison function turns the reading into a decision: upper and lower limits are entered, and the instrument indicates pass or fail with a buzzer. That is what lets it run as a sorting station without a computer.
Start with the tolerance. The digit count should be one step better than the tolerance being judged, so that the instrument’s own uncertainty is a small part of the decision rather than a large part of it. Everything else follows from that.
Then the interface. A stand-alone bench needs nothing but the front panel. A bench that is part of an automated system needs the port its software already speaks, and GPIB is not fitted to every model here.
Then the resistance work. If the smallest resistance to be measured is comparable with the lead resistance, four-wire mode is required, and that decides between the lower and higher models in the range.
Then the display. The dual VFD is quicker to read when two quantities matter at once; the colour LCD is easier when the instrument is set up once and left, and it carries the graphical views on the six-and-a-half digit model.
Finally the environment. A production bench that is never switched off and a calibration laboratory that is temperature controlled put different demands on an instrument, and the calibration interval should be agreed at the point of order rather than assumed.
Resolution is not accuracy. The digit count tells how finely the instrument displays a value; the one-year uncertainty tells how far that value can be from the true one, and the two are quoted separately for a reason. A six-and-a-half digit display with a wide uncertainty is a precise-looking wrong number.
The uncertainty figures are stated as a percentage of reading plus a percentage of range, and the second term dominates at the bottom of a range. Measuring a small signal on a high range therefore loses most of the accuracy the instrument is capable of. Manual ranging, or choosing the range that puts the reading near full scale, is what recovers it.
Bandwidth is a limit that does not announce itself. An AC reading is true-RMS only inside the stated bandwidth; above it the reading falls away without an error indication, so a switching waveform measured on a 100 kHz instrument can read low and look stable.
Four-wire resistance removes lead resistance but not thermal EMF. Where dissimilar metals meet at the terminals, a small thermal voltage adds to the reading, and the usual remedy is to take a reading in both polarities and average, or to use the instrument’s offset compensation.
Finally, the input terminals have a voltage rating and the nameplate carries a CAT rating. Neither should be read as permission to connect the instrument to a distribution circuit; a bench multimeter is a laboratory instrument, and measurements on live installation wiring belong to an instrument designed for that category.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
| TH1941 DC and AC voltage | DC 200 mV to 1000 V; AC 200 mV to 750 V, 20 Hz to 100 kHzStandard |
|---|---|
| TH1941 current | DC 2 mA to 20 A; AC 2 mA to 20 A, 20 Hz to 10 kHzStandard |
| TH1942 DC and AC voltage | DC 500 mV to 1000 V; AC 500 mV to 750 V, 20 Hz to 100 kHzStandard |
| TH1942 current | DC 5 mA to 20 A; AC 5 mA to 20 A, 20 Hz to 10 kHzStandard |
| TH1951 | DC 100 mV to 1000 V; AC 100 mV to 750 V; current 10 mA to 10 A on bothStandard |
| TH1953 | DC 100.000 mV to 1000.000 V; AC 100.000 mV to 750.000 V; AC current 100 µA to 100 mA; resistance 10 Ω to 100 MΩ at 10 mA to 500 nAStandard |
| TH1963 and TH1963A | DC 100.0000 mV to 1000.000 V; AC 100.000 mV to 750.000 V; AC current 100 µA to 100 mA; resistance 10 Ω to 100 MΩ at 10 mA to 500 nAStandard |
| TH1952 | Not stated in the material beyond its resolution and reading rateInformation required |
| DC voltage | TH1941 0.03% + 0.02%; TH1942 0.02% + 0.008%; minimum resolution 10 µVStandard |
|---|---|
| DC current | TH1941 0.08% + 0.02%; TH1942 0.05% + 0.008%; minimum resolution 100 nAStandard |
| AC voltage | TH1941 0.4% + 0.05%; TH1942 0.35% + 0.02%; minimum resolution 10 µV over 20 Hz to 100 kHzStandard |
| AC current | TH1941 0.5% + 0.3%; TH1942 0.5% + 0.08%; minimum resolution 100 nA over 20 Hz to 10 kHzStandard |
| Resistance | TH1941 0.1% + 0.025%; TH1942 0.1% + 0.008%; minimum resolution 10 mΩ at 45 nA to 0.5 mAStandard |
| Frequency | 0.01% + 0.008% on both, 5 Hz to 1 MHz, 0.0001 Hz resolution, 200 mV rms sensitivityStandard |
| Statement of uncertainty | Percent of reading plus percent of full scaleStandard |
| DC and AC voltage, current and resistance | 5 slow, 10 medium and 25 fast on TH1941 and TH1942Standard |
|---|---|
| AC plus DC | 1.2 slow, 1.4 medium and 1.5 fastStandard |
| Frequency | 1 slow, 2 medium and 3.9 fastStandard |
| 5½ and 6½ digit models | Up to 1000 readings per second is stated, without a per-function tableInformation required |
| Functions | DCV, ACV, DCI, ACI, two-wire and four-wire resistance, frequency, period, continuity, diode, dB and dBmStandard |
|---|---|
| Maths | Percent, dB, dBm and relative offset; mX+b on TH1951Standard |
| Comparison | HI, LO and IN limits with a buzzer, for pass and fail sortingStandard |
| Trigger | Internal, manual and busStandard |
| Ranging | Automatic or manualStandard |
| Display on the VFD models | Dual display, so a voltage and its frequency, or an AC and a DC component, can be shown togetherStandard |
| Stored instrument states | Ten on TH1951Standard |
| Terminals | COM, mA, A and a HI and LO pair on the front panelStandard |
|---|---|
| Front panel rating markings | 350 V MAX, 1000 V MAX, 10 A and 3 A MAX, T2AL 250 V; CAT I 1000 V and CAT II 300 V appear across the range depending on the modelStandard |
| Rear panel | USB, mains inlet with fuse, and a ground terminalStandard |
| Dimensions and weight | TH1941 235 × 105 × 360 mm at 2.4 kg; TH1951 235 × 105 × 360 mm at 2.5 kg; TH1963 235 × 105 × 320 mm at 2.7 kgStandard |
| Dimensions of TH1942, TH1952 and TH1953 | Not stated in the materialInformation required |
| Model | Configuration | Key ranges | Availability |
|---|---|---|---|
| TH1941 | 4½ digit, 21,000 counts, dual VFD, USB | DC 200 mV to 1000 V; AC 200 mV to 750 V; 2 mA to 20 A; 25 readings per second | The entry model for production checks |
| TH1942 | 4½ digit, 51,000 counts, dual VFD | DC 500 mV to 1000 V; AC 500 mV to 750 V; 5 mA to 20 A | The same body at higher resolution and tighter one-year uncertainty |
| TH1951 | 5½ digit, 119,999 counts, VFD, USB, GPIB and RS232C | DC 100 mV to 1000 V; AC 100 mV to 750 V; 10 mA to 10 A; ten stored states | The model for a bench that has to be driven over GPIB |
| TH1952 | 5½ digit, 120,000 counts, dual VFD | Not stated in the material beyond resolution and reading rate | Listed in the material with resolution and display only |
| TH1953 | 5½ digit, 119,999 counts, 4.3 inch colour LCD with an English menu option | DC 100.000 mV to 1000.000 V; AC 100.000 mV to 750.000 V; 100 µA to 100 mA AC; 10 Ω to 100 MΩ | The colour-display form of the 5½ digit model |
| TH1963 | 6½ digit, 1,199,999 counts, 4.3 inch colour LCD | DC 100.0000 mV to 1000.000 V; AC 100.000 mV to 750.000 V; 100 µA to 100 mA AC; 10 Ω to 100 MΩ | The reference grade model, with histogram, bar and trend views |
| TH1963A | 6½ digit, 1,199,999 counts, the A revision of TH1963 | Same ranges as TH1963 | Listed separately in the material; the differences from TH1963 are not stated |
Certifications are only published once a certificate copy can be produced, so this section is deliberately empty rather than populated with assumed approvals. Tell us which approvals your application requires and we will confirm what is available for this instrument.
The following are required for a complete specification but are not stated in the documentation supplied to us. They are listed rather than estimated:
It follows from the tolerance being judged, not from a preference for resolution. A 4½ digit instrument resolves and states an uncertainty that suits production checking of supplies and assemblies. A 5½ digit model is the usual choice where a reading has to be recorded against a specification with a tight limit. A 6½ digit model belongs where the instrument is part of a calibration chain and its own uncertainty has to be small compared with the item being checked.
Two quantities from the same input path - most often a voltage and its frequency, or the AC and DC components of a signal that is not a pure sine. That is what makes it useful on a power supply output or a motor drive, where the quantity of interest is rarely the fundamental alone. The colour LCD models replace this with a single larger display and graphical views.
When the resistance being measured is small compared with the lead and contact resistance, yes. A two-wire reading includes the test leads, the terminals and the contact at the probe, which on a milli-ohm measurement can be most of the reading. Four-wire mode forces current through one pair and senses the voltage across the other, so the leads drop out. It is available on the higher models in this range.
The parameters to be measured and the tolerance to be judged, which sets the digit count; the highest voltage and current that will be applied, which sets the range; whether a four-wire resistance measurement is required; and how the instrument will be controlled, since GPIB, RS232C and USB are not available on every model. Whether a calibration certificate is needed should be stated at the same time.
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