# Automotive Short and Open Circuit Tester

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Professional electricians use a variety of automotive short and open circuit tester to check a wide range of electrical functions in residential and commercial electrical wiring, and DIY homeowners will also find some of these tools useful. Learning to identify these automotive short and open circuit tester, understanding their functions, and learning how to use them will greatly expand your expertise when it comes to working on electrical wiring.

Some testers are multi-function devices that can perform most, if not all, of the common electrical testing duties, while others are single-function devices that test for a single function. Various automotive short and open circuit testers can be used to check voltage levels in both AC and DC circuits, to test for amperage, continuity, short circuits and open circuits, polarity and more. Some of these terms are unfamiliar to most homeowners, but most important for a DIYer who plans to work on home wiring knows how to test for the presence of live voltage. Several of the automotive short and open circuit tester described below fulfil that function.

## What Is An Automotive Short And Open Circuit Tester?

A automotive short and open circuit test implies that the two terminals are externally connected with resistance R=0 , the same as an ideal wire. This means there is zero voltage difference for any current value. An open circuit implies that the two terminals are points are externally disconnected, which is equivalent to a resistance R=∞ .

A short circuit implies that the two terminals are externally connected with resistance

R=0, the same as an ideal wire. This means there is zero voltage difference for any current value. (Note that real wires have non-zero resistance!)

An open circuit implies that the two terminals are points are externally disconnected, which is equivalent to a resistance

R=∞. This means that zero current can flow between the two terminals, regardless of any voltage difference. (Note that very high voltages can cause arcs of current to flow even over large air or vacuum gaps!)

### Uses Of Automotive Short And Open Circuit Tester In Practical Measurement

An ideal voltmeter is open circuit. An open circuit is a limiting approximation for a real voltmeter, which will have some large (but not infinite) resistance. An ideal ammeter is short circuit. A short circuit is a limiting approximation for a real ammeter, which will have some small (but not zero) resistance.

### Uses Of Automotive Short And Open Circuit Tester In Theoretical Analysis

Just as a voltmeter and ammeter measure by connecting two probes to a circuit, theoretical analysis is often accomplished by looking at just two nodes of a circuit.

Open and short circuit provide two useful points on the V-I curve. In particular:

The open circuit voltage is the voltage difference measured between two terminals when no current is drawn or supplied.

The short circuit current is the current that flows when the terminals are forced to have zero voltage difference.

### Automotive Short And Open Circuit Tester Test Of Transformer

Open and short circuit tests are performed on a transformer to determine the:

- Equivalent circuit of transformer
- Voltage regulation of transformer
- Efficiency of transformer
- The power required for open circuit tests and short circuit tests on a transformer is equal to the power loss occurring in the transformer.

### How Automotive Short And Open Circuit Tester Works?

The connection diagram for automotive short and open circuit tester is shown in the figure. A voltmeter, wattmeter, and an ammeter are connected in LV side of the transformer as shown. The voltage at rated frequency is applied to that LV side with the help of a variance of variable ratio auto transformer.

The HV side of the transformer is kept open. Now with the help of variac, applied voltage gets slowly increased until the voltmeter gives reading equal to the rated voltage of the LV side. After reaching rated LV side voltage, we record all the three instruments reading (Voltmeter, Ammeter and Wattmeter readings).

The ammeter reading gives the no load current Ie. As no load current Ie is quite small compared to rated current of the transformer, the voltage drops due to this current that can be taken as negligible.

Since voltmeter reading V1 can be considered equal to the secondary induced voltage of the transformer, wattmeter reading indicates the input power during the test. As the transformer is open circuited, there is no output, hence the input power here consists of core losses in transformer and copper loss in transformer during no load condition. But as said earlier, the no-load current in the transformer is quite small compared to the full load current so, we can neglect the copper loss due to the no-load current. Hence, can take the wattmeter reading as equal to the core losses in the transformer.

### Advantages Of Automotive Short And Open Circuit Tester:

The above two simple automotive short and open circuit tester offers the following advantages:

(i) The power required to carry out these automotive short and open circuit tester tests is very small as compared to the full-load output of the transformer. In case of open circuit lest, the power required is equal to the iron loss whereas, for a short-circuit test, the power required is equal to full-load copper loss.

(ii) These Automotive short and open circuit tester tests enable us to determine the efficiency of the transformer accurately at any load and p.f. without actually loading the transformer.

(iii) The automotive short and open circuit tester test enables us to determine R01 and X01 (or R02 and X02). We can thus find the total voltage drop in the transformer as referred to primary or secondary. This permits us to calculate voltage regulation of the transformer.

**Buyers Guide:**

**TOLERANCES:**

The dimensions shown in this catalog are nominal. Unless otherwise specified, tolerances are applied as follows. Tolerances do not apply to lead lengths:

± .010” for dimensions to 2 decimal places.

± .005” for dimensions to 3 decimal places.

Automotive short and open circuit tester should you have questions regarding metric system and fractional tolerances.

**CHARACTERISTICS:**

This characteristic of a fuse design refers to how rapidly it responds to various current overloads. Fuse characteristics can be classified into three general categories: very fast-acting, fast-acting,. The distinguishing feature of automotive short and open circuit tester fuses is that these fuses have additional thermal inertia designed to tolerate normal initial or start-up overload pulses.

**FUSE CONSTRUCTION:**

Internal construction may vary depending on ampere rating. Automotive short and open circuit tester photos in this catalogue show typical construction of a particular ampere rating within the fuse series.

**FUSE HOLDERS**:

In many applications, fuses are installed in fuse holders. These fuses and their associated fuse holders are not intended for operation as a “switch” for turning power “on” and “off “.

**INTERRUPTING RATING:**

Also known as breaking capacity or short circuit rating, the interrupting rating is the maximum approved current which the fuse can safely interrupt at rated voltage. During a fault or short circuit condition, a fuse may receive an instantaneous overload current many times greater than its normal operating current. Safe operation requires that the fuse remain intact (no explosion or body rupture) and clear the circuit.

Interrupting ratings may vary with fuse design and range from 35 amperes for some 250VAC metric size (5×20mm)fuses up to 200,000 amperes for the 600VAC KLK series Information on other fuse series can be obtained from the

Fuses listed in accordance with UL/CSA/ANCE 248 are required to have an interrupting rating of 10,000 amperes at 125V, with some exceptions (See STANDARDS section) which, in many applications, provides a safety factor far in excess of the short circuit currents available.

**NUISANCE OPENING**:

Nuisance opening is most often caused by an incomplete analysis of the automotive short and open circuit tester under consideration.

Of all the “Selection Factors” listed in the FUSE SELECTION GUIDE, special attention must be given to items 1, 3, and 6, namely, normal operating current, ambient temperature, and pulses. For example, one prevalent cause of nuisance opening in conventional power supplies is the failure to adequately consider the fuse’s nominal melting I2 t rating. The fuse cannot be selected solely on the basis of normal operating current and ambient temperature. In this application, the fuse’s nominal melting I2 t rating must also meet the inrush current requirements created by the input capacitor of the power supply’s smoothing filter.

The procedure for converting various waveforms into I2t Circuit demand is given in the FUSE SELECTION GUIDE.

For trouble-free, long-life fuse protection, it is good design practice to select a fuse such that the I2t of the waveforms no more than 20% of the nominal melting I2t rating of the fuse. Refer to the section on PULSES in the FUSE

**RESISTANCE:**

The resistance of a fuse is usually an insignificant part of the total circuit resistance. Since the resistance of fractional amperage fuses can be several ohms, this fact should be considered when using them in low-voltage circuits. Actual values can be obtained by contacting.

Most fuses are manufactured from materials which have positive temperature coefficients, and, therefore, it is common to refer to cold resistance and hot resistance (voltage drop at rated current), with actual operation being somewhere in between.

Cold resistance is the resistance obtained using a measuring current of no more than 10% of the fuses nominal rated current. Values shown in this publication for cold resistance are nominal and representative. The factory should be consulted if this parameter is critical to the design analysis.

Hot resistance is the resistance calculated from the stabilized voltage drop across the fuse, with current equal

### Important Features Of Automotive Short And Open Circuit Tester

* Leakage Current:* When an automotive short and open circuit tester is in a “tripped state” it protects the circuitry by limiting the current flow to a low leakage level. Leakage current can range from less than a hundred milliamps (mA) at rated voltage up to a few hundred milliamps (mA) at lower voltages. Fuses on the other hand completely interrupt the current flow when tripped, and this open circuit results in no leakage current when subjected to an overload current.

** Interrupting Rating: A**utomotive short and open circuit tester are rated for a maximum short circuit current at rated voltage also known as “breaking capacity” or Imax. This fault current level is the maximum current that the device can withstand safely, keeping in mind that the PTC will not actually interrupt the current flow (see Leakage Current above). A typical automotive short and open circuit tester rating is 40A; or for the battery strap automotive short and open circuit tester, this value can reach 100A. Fuses do in fact interrupt the current flow in response to the overload and the range of interrupting ratings, vary from tens of amperes (A) up to 10,000 (A) amperes at rated.

**Voltage**

* Operating Voltage Rating:* General use automotive short and open circuit testers are not rated above 60V while fuses are rated up to 600V.

* Hold Current Rating: *The hold (operating) current rating for PTCs can be up to 14A, while the maximum level for fuses can exceed 30A.

* Resistance: *Reviewing product specifications indicates that similarly rated PTCs have about twice (sometimes more) the resistance of fuses.

** Agency Approvals: A**utomotive short and open circuit tester are recognized under the Component Program of Underwriters Laboratories to UL Standard 1434 for Thermistors. The devices have also been certified under the CSA Component

* Time-Current Characteristic:* Comparing the time current curves of PTCs to time-current curves of fuses show that the speed of response for a PTC is similar to the time delay of automotive short and open circuit tester.

* Temperature Rerating:* The useful upper limit for automotive short and open circuit tester is generally 85ºC, while the maximum operating temperature for fuses is 125ºC. Ambient temperature effects are in addition to the normal rerating. Automotive short and open circuit tester hold and trip rating must be related when applied at conditions other than room ambient. For example, any rise in ambient temperature will decrease the hold current rating as well as the trip current. A reduction in ambient temperature will increase the trip current as well as the hold current.

The temperature derating curves in the table below compare automotive short and open circuit tester to fuses and illustrate that more rerating is required for automotive short and open circuit tester at a given temperature.

**Conclusion:**

Hope fully we have provided important information which you want before to purchase a product of your choices. Here is the complete guide to choose best automotive short and open circuit tester for your need. Hope you can find automotive short and open circuit tester online.