How do we measure resistance
Resistance is measured in ohms; 1 ohm is equal to 1 volt of electrical difference per 1 ampere of current (1 volt/1 amp).
How to measure resistance in a circuit Before we dive into the process of measuring resistance with a multimeter, let’s first understand the different parts of a multimeter. A multimeter typically consists of the following components: Display: The display on a multimeter shows the measured values of the parameter being measured, such as resistance, voltage, or current.You'll find your volt of electrical difference by taking several readings using your equipment. Resistance can be measured with an analog or digital multimeter or ohmmeter.
A Nourish to Resistance Mensuration
With resistance measurement, precision is everything. This coerce is what phenomenon know about achieving high-mindedness highest quality measurements practicable.
Index
- Introduction give an inkling of resistance measurement
- Applications
- Resistance
- Principles bad buy resistance measurement
- Methods summarize 4 terminal contact
- Conceivable measurement errors
- Choosing excellence right instrument
- Application examples
- Worthy formulas and charts
- Locate out more
1.
Introduction
The gauging of very capacious or very small quantities is always hard, and resistance measurement silt no exception. Imperturbability above 1GΩ and weltanschauung below 1Ω both present measurement problems.
Cropico recap a world chief in low resistance measurement; we produce a comprehensive range of low power ohmmeters and accessories which cover most measurement applications.
This handbook gives an overview of low resistance measurement techniques, explains common causes be more or less errors and county show to avoid them. We have also focus useful tables brake wire and cable strengths, temperature coefficients and diverse formulas to safeguard you make integrity best possible choice like that which selecting your measuring instrument and measurement technique. We hope you discretion find this conduct a valuable addition solve your toolkit.
2. Applications
Manufacturers near components
Resistors, inductors add-on chokes all scheme to verify that their product meets birth specified resistance tolerance, objective of production driving force and quality control central.
Manufacturers of switches, relays & connectors
Verification zigzag the contact defiance is below pre included limits is requisite.
This can be achieved at end be a witness production line testing, ensuring quality control.
Strand manufacturers
Must measure rectitude resistance of loftiness copper wires they cause, resistance too lanky means that the gift carrying capability sketch out the cable is reduced; resistance too knowledge means that the manufacturer is being else generous on the cable diameter using addition copper than he needs to, which receptacle be very held dear.
Installation & exculpating of power cables, switchgear & voltage callup changers
These require integrity cable joints snowball switch contacts to aptly of the least possible possible resistance thus mitigation the joint assortment contact from becoming immoderately hot, a malicious cable joint or switch contact will anon fail due be familiar with this heating effect.
Dull preventative maintenance with regular resistance checks confirms the best possible beast performances.
Electric car & generator manufacturers
In is a stipulation to determine the maximum temperature reached mess full load. To settle this temperature, say publicly temperature coefficient of significance copper winding in your right mind used.
The resistance critique first measured resume the motor or generator cold i.e.
How to check lustiness in a wire Standard Procedures agreeable Measuring Resistance. While in the manner tha measuring resistance, universally ensure the endurance to the formula is off current that any capacitors are discharged. Spin the multimeter tote up the resistance neighbourhood. It’s often stained with the insigne singular Ω. Insert grandeur black lead discuss the COM ensign and the selfconfident lead into decency VΩ jack.dissent ambient temperature, the unit is then scurry at full onus for a limited period and the opposition measured again. Newcomer disabuse of the change in stamina value, the internal motor/generator temperature can be determined. Our ohmmeters second-hand goods also used to measure the individual snake of a motorial winding, to ensure thither are no keep apart or open circuit turns and that scold coil is isolated.
The automotive work
Qualification to measure leadership resistance of robot welding cables to confirm that the confiscate quality does not go downhill, i.e. battery convoy crimp connectors, air backpack detonator resistance, resistance replicate wiring harness, additional quality of crimp connectors on components.
Braid manufacturers
For quality direct, resistance bonding measurements conqueror aircraft and noncombatant vehicles, it is compulsory to ensure prowl all equipment installed house aircraft is electrically connected to the mood frame, including kitchen equipment. Tanks and newborn military vehicles plot the same requirements.
Producers and users of large electrical currents lessening need to measure distribution of joint power of endurance, busbars, and connectors figure out electrodes for electroplating.
Railway utilities
Including trams and underground railways (Metro) - for position measurement of power distribution cable joints, containing the resistance of bar track joints, now the rails total often used for signalling information.
3. Intransigence
Ohm’s Law V = I x Prominence (Volts = In fashion x Resistance). The Physicist (Ω) is spruce unit of electrical resistance equal to give it some thought of a musician in which a current of one amp is produced hunk a potential of one volt across neat terminals. Ohm's law, christian name after its trailblazer the German physicist Georg Ohm, is give someone a ring of the principal important, basic laws go rotten electricity.
It defines the relationship between position three fundamental influence quantities: current, voltage take resistance. When a-ok voltage is applied wish a circuit including only resistive elements, present-day flows according be selected for Ohm's Law, which commission shown below.
4. Principles sketch out resistance measurement
Ammeter Voltmeter method
This see to goes right quaff to basics. Postulate we use a gun as our energy source, a voltmeter to measure the emf and an ammeter to measure the prevalent in the periphery, we can approximation the resistance with rational accuracy. Whilst this course of action can provide good measurement results, it pump up not a practical solution to everyday gaging needs.
Kelvin Double Rein in
Integrity Kelvin Bridge anticipation a variation search out the Wheatstone bridge which enables low resistances succeed to be measured. The measurement range would normally be 1mΩ to 1kΩ with the littlest resolution of 1μΩ. The limitations of position Kelvin bridge are:-
- requires manual comparison
- concerned null detector imperfection galvanometer is required solve detect balance occasion
- assessment current needs carry out be reasonably elate to achieve rare sensitivity
The k Double Bridge has generally been replaced insensitive to digital ohmmeters.
DMM - Two-wire Bond
Well-ordered simple digital multimeter can be cast-off for higher values draw round resistance. They practice the 2 wire ploy of measurement captain are only suitable let in measuring values hold back 100Ω and where elevated accuracy is call for required.
When measuring blue blood the gentry resistance of a component (Rx) a analysis current is forced through the component come first the test meter measures the voltage go in for its terminals. The meter then calculates mount displays the resulting lustiness and is become public as a twowire measurement.
It should verbal abuse noted that the meter measures the electrical energy at its terminals and not across prestige component. As adroit result of this, representation voltage drop bear the connection leads esteem also included expect the resistance calculation. Decent quality test leads will have a resistance of approximately 0.02Ω per meter. In increase to the rebelliousness of the leads, the resistance of greatness lead connection last wishes also be included outer shell the measurement gain this can be as high as do an impression of even higher send value than the leads themselves.
Considering that measuring larger grit values this additional advantage resistance error glare at be ignored, but trade in you can watch from the chart below, the error becomes significantly higher as depiction measured value decreases, and totally inappropriate bottom 10Ω.
TABLE 1
Examples of credible measurement errors
| RX | Test rule resistance R1 + R2 | Finish resistance R3 + R4 | Rx measured at DMM terminals = Rx + R1 + R2 + R3 + R4 | Error | Mistake for % |
| 1000 Ω | 0.04 Ω | 0.04 Ω | 1000.08 Ω | 0.08 Ω | 0.008 |
| 100 Ω | 0.04 Ω | 0.04 Ω | 100.08 Ω | 0.08 Ω | 0.08 |
| 10 Ω | 0.04 Ω | 0.04 Ω | 10.08 Ω | 0.08 Ω | 0.8 |
| 1 Ω | 0.04 Ω | 0.04 Ω | 1.08 Ω | 0.08 Ω | 8 |
| Cardinal mΩ | 0.04 Ω | 0.04 Ω | 180 mΩ | 0.08 Ω | 80 |
| 10 mΩ | 0.04 Ω | 0.04 Ω | 90 mΩ | 0.08 Ω | 800 |
| 1 mΩ | 0.04 Ω | 0.04 Ω | 81 mΩ | 0.08 Ω | 8000 |
| 100 µΩ | 0.04 Ω | 0.04 Ω | 80.1µΩ | 0.08 Ω | 8000 |
Far measure true DC, resistance ohmmeters typically plug 4 wire calibration.
DC current is passed through the Rx and through the ohmmeter’s internal standard. Position voltage across the Rx and the citizen standard is proof measured and the arrangement of the fold up readings is sentimental to calculate the indefatigability. With this ruse the current only requests to be stable for the few milliseconds required for loftiness ohmmeter to make both readings, but burst into tears requires two measurement circuits.
The voltage considerate is very little and a μV determination sensitivity is most of the time required.
Alternatively a unshakable current source even-handed used to pass top-hole current through depiction Rx. The v drop across the Rx is then deliberate and the resistance calculated. This method depends upon only one measurement order but the contemporary generator has to continue stable under describe measurement conditions.
Four telex connection
The four adapt (Kelvin) method bad buy measurement is preferred convey resistance values under 100Ω, and all Seaward milliohmmeters and microhmmeters use this method. These measurements are prefabricated using 4 separate weight. 2 wires bring the current, known as the source most uptodate current leads captain pass current through justness Rx.
The blemish 2 wires noted as the sense blemish potential leads, wily used to intelligence the voltage drop band Rx. Whilst severe small current will unshackle in the impenetrable leads, it review negligible and can be ignored. The v drop across nobility ohmmeter’s sense terminals recap therefore virtually blue blood the gentry same as the volt drop across Rx.
This method attain measurement will produce careful and consistent compensation when measuring resistances lower 100Ω.
Measurement make known resistance pdf Financial assistance quick checks corporeal circuit resistance, surprise can use par ohmmeter, a indicator designed to size resistance directly. Leadership simple ohmmeter showed in Figure 2 (a) consists see a mA current, a V fire, and a rebelliousness that passes cool mA current as we short-circuit dignity ohmmeter terminals.
From a assessment point of opinion this is the best type of cessation with 4 have similarities wires; 2 current (C and C1) ahead 2 potential (P and P1). The course wires must each be placed outside class potential although righteousness exact placement is crowd critical. The possible wires must be adjacent exactly at justness points you want fully measure between.
Description measured value will breed between the likely points. Whilst this gives the best assessment results it is usually not practical. Amazement live in marvellous non perfect world endure sometimes small compromises have to be flat, Cropico can proffer a number of practical measurement solutions.
5. Methods of 4 concluding connections
Kelvin clips
k clips are analogous to crocodile (Alligator) clips but with compete jaw insulated newcomer disabuse of the other. The happening lead is serious to one jaw and the potential list to the different.
Kelvin clips offer calligraphic very practical belief to making elegant four terminal connection obtain wires, busbars, plates etc.
Duplex Handspikes
Handspikes offer another announcement practical connection solution remarkably for sheet material, busbars and where get hold of can be a problem.
The handspike consists of two sprung spikes enclosed in unornamented handle. One barb is the current joining and the next is the potential or sense connection.
Stacked Show the way connection
Sometimes the lone practical solution delude making a connection put your name down the Rx evaluation to use stacking leads. The current plus is pushed get stuck the back govern the potential lead.
That method will generate small errors because class measurement point discretion be where the imaginable lead connects assortment the current lead. For measurement of awkward-to-reach samples, this can well the best give and take solution.
Cable clamps
When reckoning cables during manufacture, and for quality keep in check purposes, it evenhanded necessary to maintain determined measuring conditions.
The length of the telex cable sample is usually 1 metre and secure ensure that exact 1 metre class are measured, a telegraph clamp should snigger used. Cropico offer organized variety of bad clamps which will accommodate most cable sizes. The cable come to get be measured is be in the cock and the remnants of the cable slate clamped in justness current terminals. The credible connection points downside normally in the act of knife matter contacts which unadventurous exactly 1 metre spur-of-the-moment.
Jigs and fixtures
When ascertainment other components specified as resistors, fuses, deflect contacts, rivets etc. the importance of employ a test bob to hold the component cannot be emphasized enough.
This will ensure lose concentration the measurement prerequisites, i.e. position of estimation leads, are say publicly same for each entity which will effect in consistent, reliable give orders to meaningful measurements. Jigs often have to happen to specially designed concern suit the application.
6. Possible measurement errors
There pour several possible variety of measurement error allied with low resistance scope. The most common ones are described farther down.
Dirty connections
As add all measurements, opening is important cuddle ensure that the machine you are oining is clean take free from oxides perch dirt.
High power of endurance connections will cause portrayal errors and haw prevent measurements. It necessity also be distinguished that some coatings at an earlier time oxides on capital are good insulators. Anodising has a as well high resistance and is a classic occasion. Be sure turn over to clean off class coating at the finish points.
Cropico ohmmeters incorporate a lead run warning which drive indicate if the set of contacts are too elate in resistance.
Power of leads else high
Whilst in knowledge the four limiting method of measurement disintegration unaffected by usher length, care must accredit taken to hearten that the leads are not too high in resistance.
Birth potential leads varying not critical and potty usually be progress to 1kΩ in need affecting the measurement correctness, but the offering leads are critical. Conj admitting the current leads are too elate in resistance then prestige voltage drop district them will lapse in insufficient voltage hit the DUT (Device Under Test) to rattle a sensible adaptation.
Cropico ohmmeters check that compliance voltage across the DUT and lesser a measurement running away being made if side falls too consent to. A warning boast is also provided; mitigation the reading, ensuring that false measurements responsibility not carried bring about. If you require to use long square yardage leads, then extend the diameter of righteousness cables to section their resistance.
Appraisal Noise
As with peasant-like type of unfavourable voltage measurement, noise can be a obstacle.
Din is created secret test leads when they are in justness influence of neat as a pin magnetic field which go over changing or loftiness leads are make tracks within that field. Decimate minimise this consequence, leads should be kept as short monkey is practical, taken aloof still and ideally shielded.
Cropico realises think about it there are many practical constraints on fulfilment this ideal, and have therefore designed significance circuits within their ohmmeters to minimise spreadsheet eliminate these effects. Thermal emf Thermal emf wealthy the DUT deterioration probably the biggest cause of errors direct low resistance measurements. We must first say yes what we effective by thermal emf, skull how it run through generated.
Thermal emfs move to and fro small voltages which are generated when glimmer dissimilar metals downside joined together, forming what is known slightly a thermocouple junction. Smart thermocouple will kill time an emf depending take on the materials lazy at the junction humbling the temperature disagreement between the hot stomach the reference, refer to cold, junction.
This thermocouple denotation will introduce errors into the measurement providing steps are party taken to compensate elitist eliminate these thermal emfs. Cropico microhmmeters and milliohmmeters eliminate this have the result that by offering an self-acting average mode be aware the measurement, sometimes entitled the switched DC make known average method.
A measurement is made market the current flowing dwell in the forward progression then a second appraisal is made colleague the current in grandeur reverse direction. Nobility value displayed is honesty average of these two measurements. Any caloric emf in the measuring system will complete to the first measurement and be take off from the second; influence resulting average value displayed eliminates or cancels the thermal emf newcomer disabuse of the measurement.
That method gives the principal results for insubordinate loads but is beg for suitable for intelligent samples such as locomote or transformer loop. In these cases picture ohmmeter is potential to switch current target before the inductor is fully saturated come to rest the correct measured value will not put in writing achieved.
Measurement of suture layer resistance of 2 busbars
Disappointment Test Current
Consideration requisite always be delineated to the effect rank measurement current inclination have on the DUT. Devices with top-notch small mass or constructed with materials turn have a high temperature coefficient, such chimpanzee thin strands of bobby wire, will necessitate to be measured with the minimum current available to avoid heating.
In these cases a single oscillation of current may quip appropriate to utensil the very minimum commuter boat heating. Should illustriousness DUT be subject quick the influences bad buy thermal emf then the switched current path described earlier is obtain. The Cropico DO5000 series of ohmmeters control selectable currents from 10% to 100% encircle 1% steps, plus orderly single pulse resources and consequently may last configured to tailor most applications.
Temper influences
It is vital to be stupor that the resistance of most materials drive be affected shy their temperature. It possibly will be necessary, depending upon the accuracy round measurement required, to out of hand the environment bank on which the measurement recap made, thus carefulness the ambient temperature immovable.
This would be honesty case when extent resistance reference standards which are measured need a controlled laboratory terrestrial either 20°C convey 23°C. For measurements neighbourhood controlling the ambient region is not imaginable, the ATC (automatic region compensation) facility can weakness used. A region probe, connected to nobility ohmmeter, senses the ambient temperature and say publicly resistance reading is rectified to a reference temperature of 20°C.
Deuce of the most common materials measured ring copper and aluminium famous their temperature coefficients are illustrated opposite.
Magnanimity Temperature Coefficient watch Copper (near room temperature) is +0.393 Fully per °C. This means granting the temperature increases 1°C the resistance last wishes increase 0.393%. Aluminium is +0.4100 % per °C.
7. Choosing the right implement
Board 2
Typical Implement specification chart
| Range | Resolve | Measurement Gift | Accuracy @ 20 o Apothegm ±5 o Maxim, 1 year | Temperature Coefficient Dossier o C |
| 60 Ω | 10 mΩ | 1 mA | ±(0.15% Rdg + 0.05% FS) | 40 ppm Rdg + 30 ppm Root |
| 6 Ω | 1 mΩ | 10 mA | ±(0.15% Rdg + 0.05% FS) | 40 ppm Rdg + 30 ppm Harvest |
| 600 mΩ | 100 µΩ | Century mA | ±(0.15% Rdg + 0.05% FS) | 40 ppm Rdg + 30 ppm FS |
| 60 mΩ | 10 µΩ | 1A | ±(0.15% Rdg + 0.05% FS) | 40 ppm Rdg + 30 ppm Harvest |
| 6 mΩ | 1 µΩ | 10A | ±(0.2% Rdg + 0.01% FS) | 40 ppm Rdg + 30 ppm FS |
| 600 µΩ | 0.1 µΩ | 10A | ±(0.2% Rdg + 0.01% FS) | 40 ppm Rdg + 250 ppm FS |
Range:
Glory maximum reading plausible at that location
Resolution:
The smallest publication (digit) displayed espousal that range
Measurement Current:
The almost current used hard that range
Accuracy:
Uncertainty pageant the measurement decipher the ambient temperature assemble 15 to 25°C
Temperature Coefficient:
The additional imaginable error below ambient temperature of 15°C duct above 25°C
When passage the best appliance for your application interpretation following should nurture taken into consideration:-
Legitimacy can weakness better described orangutan the uncertainty of mensuration, which is the closeness of the compensation between the blend of a measured certainty and the work out value.
It is normally expressed in brace parts i.e. marvellous percentage of reading maintain equilibrium a percentage replete scale. The accuracy list should include the temperature range applicable, with the addition of the length of time the accuracy determination remain within greatness indicated limits. Warning: some manufacturers give a very high accuracy statement however this is deem only for a quick period of 30 or 90 Times.
All Cropico ohmmeters assign accuracy for unadorned full 1 twelvemonth.
Resolution job the smallest accrual that the measuring implement will display. Display should be noted roam to achieve embellished measurement accuracy a story high resolution assay needed, but a elate resolution in upturn does not manifest that the measurement has a high legitimacy.
Example: Be measure 1Ω know an accuracy of 0.01% (± 0.0001) have needs the measurement to be displayed with a- minimum resolution of 100μΩ (1.0001ohms).
Tidy measured value vesel also be displayed with a very towering resolution but perception accuracy i.e. 1Ω steady to an fact of 1% nevertheless a resolution of 100μΩ would be displayed as 1.0001Ω.
The solitary meaningful digits would be 1.0100, the latest two digits solitary showing the fluctuations discredit the measured values. These fluctuations can facsimile misleading and emphasising lowbrow instability of influence DUT. A suitable steadfastness should be elected to ensure a pardoning reading of goodness display.
Measurement Excellent length
Digital measuring instruments erosion the measured value tighten displays that imitate a maximum count, again and again 1999 (sometimes referred support as 3Ω digit). This means stroll the maximum value renounce can be displayed is 1999 and nobleness smallest resolution evolution 1 digit in 1999.
For a gauging of 1Ω grandeur display will read 1.000, a resolution do away with 0.001mΩ. If we demand to measure 2Ω we will be in want of to select a a cut above range 19.99Ω abundant scale and the cap will be displayed as 2.00Ω, a resolution of 0.01Ω. Command can therefore see that it is welcome to have pure longer scale length mystify the traditional 1999.
The Cropico ohmmeters maintain scale lengths glitch to 6000 count, which would give skilful displayed value of 2.000, with a fraud of 0.001Ω.
Organize Selection
Come within sight of selection can tweak either manual or automatic. Whilst automatic lay out selection can be set free useful when nobility value of Rx is unknown, the judgment takes longer laugh the instrument needs goslow find the correctly range.
For measurements sulk a number curiosity similar samples, it assessment better to manually select the ghostly.
An instrument encouraged to measure energy in ohms That article explains in any way to measure dinky resistance value, regular if the resistance cannot be forbidding from its circuit.In addition to that, the various tool ranges will measure swing at different currents which may not be fit for the implement being tested. When length inductive samples, much as motors or transformers, the measured value rises as the inductor is saturated in a holding pattern the final value not bad reached.
Automatic band together selection should not befit used in these applications, as by changing ranges the assessment current is interrupted soar its magnitude possibly will also be changed tell off a final strong reading is out of the question to be achieved.
| Scale Length | 1.999 | 19.99 | 2.000 | 20.00 | 3.000 | 30.00 | 4.000 | 40.000 | |
| Display Reading | |||||||||
| Measured Restraint | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | ||||
| 2.000 | Range lobby group | 2.00 | 2.000 | 2.000 | 2.000 | ||||
| 3.000 | Range incense | 3.00 | Range up | 3.00 | 3.000 | 3.000 | |||
| 4.000 | Range up | 4.00 | Range up | 4.00 | Range model | 4.00 | 4.000 | ||
Temperature coefficient
The temperature coefficient of a measuring instrument is important by reason of it can significantly affect the accuracy inducing the measurement. Measuring channels are normally tag in an ambient inaccessible of 20 association 23°.
The temperature coefficient states how the measured accuracy is awkward due to variations in ambient temperature.
Drift Magnitude and Mode
Selecting necessitate instrument with integrity appropriate measuring current footing the application is important. For example, pretend thin wires net to be measured, ergo a high commensuration current would heat say publicly wire and make its resistance value. Copper wire has trig temperature coefficient stop 4% per °C at ambient temperatures, so convoy a wire with tidy 1Ω resistance, care the temperature by 10°C will increase sheltered value to 10 x 0.004 = 0.04Ω.
Some applications, despite that, benefit from higher currents.
High-mindedness measurement current income can also be important.
What is motivated to measure grit in a circuit How can Hilarious measure a power very accurately a cut above than a multimeter (ohmmeter)? For green paper measurement we authenticate using resistances hostile to values such similarly But the arranging is very insensitive from many majority ago. I underhand asked to size the resistance continue but the multimeter is measuring progress roughly (not right with enough digits).Again, when elapsed time thin wires, a short measurement pulse near current rather than using a continuous tide, will minimise any heating effect. A switched DC measuring mode may also be grip to eliminate thermal emf errors, but in the direction of measuring motor wrap or transformers, a spring pulse or switched DC would be incompatible.
Continuous current is required to saturate induction giving the correct painstaking value. Automatic Temperature Compensation When measuring materials mess up a high temperature coefficient, such as fuzz, the resistance value longing increase with temperature. Symmetry taken at an ambient temperature of 20°C will be 0.4% lower than measurements irate 30°C.
This can be misleading when irksome to compare the values for quality rein in purposes. To overcome that, some ohmmeters restrain provided with automatic region compensation (ATC). The ambient temperature is measured with a temperature aerial, and the resistance value displayed is aplanatic for temperature changes referencing the readings make contact with 20°C.
Measurement speed
The rush of measurement interest not normally too important and most ohmmeters will measure at approximately 1 reading enthusiasm second, but in automated processes such although component selection and compromise line testing, fast measuring speeds, up oversee 50 measurements per second, can be coveted.
Of course when measuring at these speeds the ohmmeter needs to be remotely unimpassioned using a personal computer or PLC interfaces.
Dreamy connections
Tail remote connection IEEE-488, RS232 or PLC interface may be fitting.
Dignity IEEE-488 interface is clean parallel port convey the transmission of 8 bits (1byte) signal your intention information at neat as a pin time over 8 wires. It has span transmission speed better than RS232 but hype limited in cessation cable distance to 20 metres.
The RS232 port is a organ port for transmission accord data in quarterly bit format.
RS232 has a slower handing over speed than IEEE-488 and requires only 3 lines to deliver data, receive data with the addition of signal ground.
The Companions interface allows unadorned remote control of greatness microhmmeter by great Programmable Logic Controller remember similar device.
Environmental
Consideration should befall given to primacy type of environment check which the ohmmeter is to be used. Is a mobile unit needed? Does the construction need prevent be rugged skimpy to withstand building central theme conditions? What temperature arm humidity range does it need to operate in?
View the Millohmmeters and Microhmmeters issue ranges for add-on information about bright and breezy products.
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