Resistance P.O. Box Manufacturer,Supplier and Exporter in India
Product Code : EL-SI-8106
Jlab Export is a leading Resistance P.O. Box Manufacturer,and suppliers in India
Resistance P.O. Box (code EL-SI-8106) is a Post Office box–type resistance box for Wheatstone bridge resistance measurements in school and college physics labs. Its coils are wound with constantan, with the accuracy listed as +0.1%, and the box is built on 12 mm thick rectangular brass blocks. It is made by Jain Laboratory Instruments Pvt Ltd (JLab) at its works in Ambala, India.
Specifications
| Parameter | Detail |
|---|---|
| Type | Post Office (P.O.) box resistance box |
| Coil wire | Constantan |
| Accuracy | +0.1% (as listed) |
| Brass blocks | Rectangular, 12 mm thick |
| Quality check | Each P.O. box is visually inspected before dispatch |
| Pack quantity | Each (sold individually) |
| Minimum order quantity | 10 units |
| Dispatch time | Usually 7–10 working days |
| Product code | EL-SI-8106 |
| Manufacturer | Jain Laboratory Instruments Pvt Ltd (JLab) — OEM |
| Country of origin | India (made in Ambala, Haryana) |
How Does It Compare with Other JLab P.O. Boxes?
| Model | Coil wire | Listed accuracy | Brass blocks |
|---|---|---|---|
| This P.O. box (EL-SI-8106) | Constantan | +0.1% | 12 mm thick, rectangular |
| P.O. Box Ratio Constantan Coil | Constantan | Within ±0.1% | 14 mm thick, rectangular |
| Resistance P.O. Box 4 | Manganin | ±0.02% to 0.005% (as listed) | 14 mm thick, rectangular |
This box suits routine Wheatstone bridge practicals with constantan coils. The P.O. Box Ratio model has the same coil wire on thicker blocks, and the manganin P.O. Box 4 is the choice where a tighter listed accuracy matters.
What Is the Resistance P.O. Box Used For?
A P.O. box is a Wheatstone bridge built into a box: two ratio arms and a third, adjustable arm of resistance coils, each coil brought into the circuit by pulling out the brass plug that shorts it between two blocks. With a cell, a galvanometer and the unknown resistance connected, students choose a ratio, then adjust the plugs in the third arm until the galvanometer shows no deflection, and calculate the unknown from the ratio and the arm value; repeating with a larger ratio narrows the result. The method is used to find the resistance and specific resistance of a wire in school and college physics practicals. Constantan is used for the coils because its resistance changes very little with temperature. Push each plug in with a slight twist so it seats firmly, keep plugs and blocks clean, since dirt adds contact resistance, and keep all plugs in place when the box is stored.
Frequently Asked Questions
What accuracy do the coils have?
The listing gives +0.1% for the constantan-wound coils.
What resistance values and ratio arms does it have?
They are not stated in this listing. Ask JLab for the coil values, ratio arms and plug layout of the box you are quoted, or send the values your practical manual uses.
How does it differ from the Resistance P.O. Box 4?
This box uses constantan coils on 12 mm brass blocks with accuracy listed as +0.1%; the P.O. Box 4 uses manganin coils on 14 mm blocks, with its accuracy listed as ±0.02% to 0.005%.
Who manufactures this P.O. box?
Jain Laboratory Instruments Pvt Ltd (JLab) makes it at its works in Ambala, Haryana, India.
OEM Manufacturer
JLab is the trading name of Jain Laboratory Instruments Pvt Ltd, a physics lab instruments manufacturer in India, incorporated in 2017 and based on Hargolal Road, Ambala, Haryana. The P.O. box is made at JLab’s own works, not bought in from a trader, so schools, colleges, dealers and importers buy factory-direct and repeat orders are handled by the manufacturer. JLab exports worldwide and ships to buyers in every region — for example Zambia in East Africa, Papua New Guinea in Oceania, Lithuania in Northern Europe, Japan in East Asia and Oman in the Middle East. Tender buyers will find details on the JLab lab tenders page.
Related Bridge Equipment
- Resistance P.O. Box 4 — the manganin-coil P.O. box on 14 mm brass blocks.
- P.O. Box Ratio Constantan Coil — a constantan P.O. box listed in Ratio 3 and Ratio 4 versions.
- Resistance Box Constantan & Manganin — a dial-switch decade resistance box in two grades.
- Spot Reflecting Galvanometer — a DC null detector for Wheatstone bridges and potentiometers.
- Portable Wheatstone Bridge — a self-contained bridge with built-in galvanometer.
More in the Scientific Instrument range and the Indian Instruments section.
Request a Quote
Quotes come direct from the manufacturer. Use the Add To Cart enquiry button on this page, or send the quantity (minimum 10 units), the coil values you need and your delivery location through the contact page.
Last updated: 8 October 2026
