Electrical Test & Measurement · Electrical Test Equipment
Four-terminal conductor testers that read resistance, resistivity and conductivity on wire and bar from 0.02 mm diameter, with 0.02% basic accuracy and up to 10 A test current.
SJ5511 (2 models) ·
A conductor is bought by cross-section and checked by resistivity. The resistance of a one-metre sample tells you nothing on its own, because it depends on how long the sample is; the resistivity does not. Getting from one to the other is arithmetic, and arithmetic done by hand at a bench is where the errors live.
Two bench instruments, both four-terminal, both measuring resistance, resistivity and conductivity at the same time and displaying 5½ digits on a colour screen.
The smaller one reads 0.1 µΩ to 10 MΩ with a test current up to 1 A on a 4.3-inch display. The larger reads 0.01 µΩ to 10 MΩ with up to 10 A on a 7-inch display. Both accept the same optional milliohm fixture, which takes wire and bar from 0.02 mm to 42 mm, and both carry HANDLER, RS232, RS485 and USB host as standard.
The difference between them is where the resolution is needed. A hook-up wire of a metre has enough resistance for the 1 A model; a short length of heavy stranded conductor or a busbar does not, and that is what the 10 A output is for.
Four terminals are used. The drive pair passes a known current through the conductor; the sense pair measures the voltage between two points a measured distance apart. Because the sense pair draws almost no current, the clip and contact resistance do not enter the reading, and the instrument obtains the resistance of the length between the potential probes.
Resistivity follows from that resistance multiplied by the cross-section and divided by the length. The operator enters the conductor size and the gauge length, or the diameter from which the instrument derives the section, and the display shows resistivity directly. Conductivity is its reciprocal, in the units the conductor trade uses.
The temperature enters because resistivity does. Copper rises by roughly 0.4% per degree, so a workshop that swings ten degrees moves the reading by four percent, which is more than the instrument’s accuracy. The temperature compensation converts the measured resistance to a chosen reference temperature, and the instrument displays the ambient it measured so that the conversion can be checked.
Start with the conductor size and length that the fixture will hold. A milliohm fixture with potential probes at a fixed spacing sets the length, and the same fixture has to accept the largest and smallest conductor in the range. If the bench sees 0.05 mm wire and 25 mm bar, the fixture is two fixtures.
Then the resistance at the bottom of the range. A metre of 1 mm² copper is about 17 mΩ, which either model reads easily. A 100 mm length of 240 mm² conductor is around 18 µΩ, which needs the 10 A model to resolve properly. The crossover is roughly where the expected resistance falls below 100 µΩ.
Then the accuracy the standard calls for. It is the same 0.02% on both models in the parameter table, so accuracy does not separate them; the current does.
Then the calculation inputs. A resistivity result is only as good as the section and the length entered, and the section of a stranded conductor is not the sum of the strand diameters unless the stranding is compacted. The instrument cannot know that, so the method has to state whether nominal or measured section is used.
Finally the record. Both models store ten setups and both can send results over serial or to a USB stick, which matters when a batch has to be traced back to a delivery.
The measurement is of the conductor between the potential probes, not of the whole reel. A reel with a bad joint somewhere outside that span will pass, and a test that is meant to find joints has to be arranged to include them.
Temperature is the largest systematic error. Compensating to 20 °C is a calculation, and it assumes a coefficient for the material. Aluminium and copper differ, and an alloy differs from both; using the wrong coefficient moves the result by more than the instrument’s accuracy across a normal working range.
Self-heating matters at 10 A. A thin conductor carrying 10 A dissipates enough power to warm itself during the measurement, and the reading then drifts downward as the resistance rises. The current has to be matched to the conductor, not set to the instrument’s maximum.
Contact quality at the potential probes is the other limit. Four terminals remove the clip resistance from the reading, but a probe that only touches an oxide layer sees a voltage that is not the conductor’s. Cleaning the contact area, or using a fixture that penetrates the surface, is part of the method rather than an optional refinement.
Finally, the geometry. Resistivity computed from a nominal section is a comparison against a specification; resistivity computed from a measured section is a material property. The two are not the same number, and a report should say which one it contains.
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.
| Measurement parameter | Resistance, resistivity and conductivityStandard |
|---|---|
| Resistance range | 0.1 µΩ to 10 MΩ; 0.01 µΩ to 10 MΩ on the larger modelStandard |
| Resistivity range | Depends on the resistance range and on the dimensions of the itemStandard |
| Basic accuracy | 0.02% in the parameter table for both models; the larger model's card prints 0.05%Standard |
| Resolution | 0.01 µΩ on the larger model; 0.1 µΩ on the smallerStandard |
| Test current | ≤1 A; ≤10 A on the larger modelStandard |
| Measurement speed | 30 readings per second fast, 15 medium, 3 slowStandard |
| Thermal EMF cancellation | Fitted on both modelsStandard |
| Zeroing | Self-stabilising zero, no routine zeroing; short-circuit zeroing availableStandard |
| Reading digits | 5½ digits on both modelsStandard |
| Conductor forms | Wire and bar, solid or strandedStandard |
|---|---|
| Diameter range with fixture | 0.02 mm to 42 mmOptional |
| Length and section entry | Length and cross-section entered for the resistivity calculation; diameter can be entered directly on the display shownStandard |
| Supplied clip | SJ55010 four-terminal Kelvin clipStandard |
| Milliohm fixture | Optional fixture for wire and bar, selected to the conductor sizeOptional |
| Comparator | Three levels, HI, PASS, LO and FAIL outputStandard |
|---|---|
| Beeper | Pass, fail or offStandard |
| Limit entry | Absolute upper and lower limits, or percentage limits with a nominal valueStandard |
| Interfaces | HANDLER, RS232, RS485, USB host and USB deviceStandard |
| USB host | Memory stick for results and for firmware updateStandard |
| Stored setups | 10 groupsStandard |
| Trigger sources | Internal, external and manualStandard |
| Temperature compensation | Fitted, referenced to a set ambient temperature; temperature accuracy 0.1 °CStandard |
|---|---|
| Temperature display range | −10 to 99.9 °CStandard |
| Operating environment | 0 to 40 °C, ≤90% RH without condensationStandard |
| Body, smaller model | 264 × 108 × 370 mm, about 4 kg in the parameter table; 336 × 87 × 216 mm on the outline drawingInformation required |
| Body, larger model | 350 × 130 × 400 mm, about 10 kg; 400 × 130 × 350 mm on the outline drawingInformation required |
| Mains | 198 to 242 V AC, 47 to 63 Hz in the parameter table; 90 to 242 V AC on the smaller model's inlet markingInformation required |
| Model | Configuration | Key ranges | Availability |
|---|---|---|---|
| SJ5511 | Compact conductor tester, 4.3-inch display | 0.1 µΩ to 10 MΩ; test current ≤1 A; 0.02% basic accuracy | 5½ digits; 10 stored setups; about 4 kg |
| SJ5510 | Large conductor tester, 7-inch display, 10 A output | 0.01 µΩ to 10 MΩ; test current ≤10 A; 0.02% in the parameter table, 0.05% on the model card | For heavy conductors and very low resistance; about 10 kg |
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:
Because resistivity is a material property and resistance is not. The instrument measures the resistance between two potential probes a known distance apart, then divides by that length and multiplies by the cross-section. That is why the gauge length and the conductor size have to be entered: the same copper will read a different resistance over 1 m than over 100 mm, but the same resistivity.
Because copper changes resistivity by roughly 0.4% per degree, which is larger than the accuracy of the instrument over a workshop's temperature swing. A reading taken at 10 °C and one taken at 30 °C differ by about 8% on the same conductor. The temperature compensation converts the measured value to a chosen reference temperature, and it is only as good as the temperature measurement and the coefficient used.
Resolution on short, thick conductors. The voltage across a 0.1 µΩ joint at 1 A is 0.1 µV, which is at the edge of what the input can resolve; at 10 A the same joint produces 1 µV and the last digits become usable. For a 1 mm wire of a metre or so, 1 A is more than enough and the larger instrument adds nothing.
The conductor material and the temperature reference the standard uses; the size range, which fixes the fixture; the length between potential probes that the fixture will impose; whether the result must be recorded or used to sort; and the ambient temperature range of the test area.
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