Why is a Zero Ohm Resistor used instead of a Jumper Wire?
Table of Contents
What is Zero Ohm Resistor?
A Zero Ohm Resistor (also known as Zero Ohm Link) is a passive device which has ideally “0 Ω” resistance like any other short wire and pure conducting materials.
0-Ω Resistor is a jumper or any other wire packaged the same like the shape of a resistor. It has almost 0-Ω resistance (although it has some resistance in real life as like other conducting materials and ± tolerance). Zero ohms resistors are available in a range such as 1/8W having 4mΩ and 1/4W having 3mΩ.
Many of us have seen these “Zero-Ohm” resistors in the modern PCB design and circuit. So one must ask about “What is the purpose of a zero ohm resistor and why 0-Ω Resistors are used instead of jumpers or wires?” Well, we will discuss the different reasons behind the story.
Types of Zero Ohm Resistors
Zero ohms resistors are available in the following two shapes.
Wire Wound Zero Ohm Resistor
Surface Mount (SMD) Zero Ohm Resistor
Wire Wound Zero Ohm Resistor
It is the general shape of an ordinary resistor. In the wire wound zero Ω ohm resistor, there is only and only one black line ( single black band) printed on the resistor. The single black strip o-ohm resistor is shown in the following fig.
Surface Mount (SMD) Zero Ohm Resistor
In the recent technology, surface mount resistors are used instead of wire wound or any other types of resistors due to the cost, simplicity and covered area of PCB board etc. In a zero ohm surface mount resistor, the manufacturer prints a “single zero “0” or “three zeros “000” on the surface. The single and three zeros labeled zero ohms resistors can be seen in the following fig.
Good to know: SMD stands for “Surface Mount Device”. We have discussed in the previous post about how to to find the value of SMD Resistors with color codes.
Why a Zero Ohm Resistor used instead of Wire?
There are multiple reasons to do so. Some of the zero ohm resistors application are as follow:
Automatic Placement by Insertion Machines
In PCB mass production, an automatic insertion machine is used to pick and place the components and devices such as diodes, capacitors, inductors, resistors etc. For the ease and reduce the production cost, it is an easy approach to use zero ohm resistors instead of wires and jumpers because you will have to manage another automatic wire placer machine or you will have to manually place it. In other words, you will have to use two machines, one for components and other one for wires and jumper which leads to a costly production and more time needed to fully assemble the PCB.
Single Layer PCB Design
A single layer PCB is less costly as compared to the double layer PCB design and assembly. To use wires in the single PCB assembly, you will have to make holes which turns it in double layer PCB. Instead of doing so, a 0-Ω resistor is the perfect match as compared to the wires and jumpers used in the single layer PCB structure. Hence, it reduces the overall cost again.
Preventing Copycats using Reverse Engineering
Yes, they exist. Copycats simply copy the well known PCB designs using reverse engineering tactics. In this case, zero ohm resistors are the best alternative to wires which confuse and prevent the copycats. To do so, designers and manufacturers put 0-Ω resistors with no marking or use different resistor color codes. This way, the chances of copying a PCB design are lesser with more efforts.
Should I Use a 0-Ω Resistor or Jumper Wire?
Well, if you are a hobbyist and just love making PCB designs and circuits for your own purposes, It is better to take the soldering iron and place a wire instead of picking those tiny so called 0-ohm resistors (they are having little bit resistance).
If you are doing mass production and working on a brand, you must use 0-Ω resistors instead of jumpers as all of your competitors are doing the same due to the above mentioned reason and advantages.
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Using zero ohm resistors reduce the cost of jumper wires insertion. For mass production, it's important to keep the cost down. Using an additional machine for jumper wires results in a separate setup and process cost. Therefore, a zero-ohm resistor is the perfect alternative that saves cost and time in assembly.
During circuit design, particularly in mixed circuits involving digital and analog components, it's often required to have separate grounds with a single-point connection. A zero-ohm resistor can be employed to connect these two grounds instead of directly joining them.
Zero ohm resistors can also be used as configuration jumpers or in places where it should be easy to disconnect and reconnect electrical connections within a PCB to diagnose problems. The resistance is only approximately zero; only a maximum is specified, which is typically in the range of 10–50 mΩ.
Zero ohm resistors are often used as jumpers to enable various circuit options because they can easily be added or omitted. They can also be used as crossovers where one trace has to cross over another trace. There are also very low resistance resistors with precise values that are used for measuring current.
That is to say, the resistance value of 0 ohm is less than or equal to 50mΩ. We often see a resistance of 0 ohms in the circuit. For novices, they are often confused: since it is a resistance of 0 ohms, that is a wire, why should it be installed?
Zero-ohm resistors have several benefits over a simple bit of cable: They can be used as a wire link and can be inserted automatically by PCB assembly robots. They come on a reel so no additional setup is required. They can be used where a resistor may be or was used in certain design variations.
To conserve its battery, an ohmmeter should never be left on the ohms function when not in use. Since the current available from the meter depends on the state of charge of the battery, the DMM should be zero adjusted to start. This may require no more than a test of touching the two probes together.
If your multimeter reads 0 ohms, it means that there is perfect continuity in the wire, fuse, battery, or device. Most multimeters will beep continuously when testing a connection with good or perfect continuity. A constant 0 indicates a perfect connection.
Zero and span adjustability is used to recalibrate the output of the sensor at the extremes of its calibrated range. Typically, these adjustments are made through potentiometers or other adjustment tools (i.e., a reed switch with a magnet) to finetune the output signal at both the zero and full span measurement points.
As you have noticed, zero ohm resistors are somewhat different. The power rating is the same as for the other resistors in the same package. so if you have a 1206 sized zero ohm resistor its power rating is the same as all other 1206 SMT resistors, 1/8 of a watt.
Since, the current flows in the closed switch or closed circuit, there is no opposition or minimal opposition in the flow of current through the circuit. This implies, that the resistance of the circuit will be minimal or negligible i.e. zero ohms.
Answer. For a resistor component such as a SMD resistor, the 0 resistor is basically specified as DC resistance, not AC impedance. The accuracy of the 0 resistor at DC should be tested by using a precise digital multi-meter (DMM) such as the 34420A.
A 0 ohm resistor can effectively suppress noise interference, with no restriction on the frequency band, and no restriction on the volume. Therefore, it is widely used.
As you have noticed, zero ohm resistors are somewhat different. The power rating is the same as for the other resistors in the same package. so if you have a 1206 sized zero ohm resistor its power rating is the same as all other 1206 SMT resistors, 1/8 of a watt.
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