Resistance P.O. Box 4 Manufacturer,Supplier and Exporter in India
Product Code : EL-SI-8109
Jlab Export is a leading Resistance P.O. Box 4 Manufacturer,and suppliers in India
Resistance P.O. Box 4 (code EL-SI-8109) is a manganin-coil Post Office box for Wheatstone bridge resistance measurements in college and school physics labs. It is built on 14 mm thick rectangular brass blocks, its accuracy is listed as ±0.02% to 0.005%, and a P.O. Box 3 version with manganin coils is offered alongside it. 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 | Manganin |
| Accuracy | ±0.02% to 0.005% (as listed) |
| Brass blocks | Rectangular, 14 mm thick |
| Versions | Resistance P.O. Box 3 and Resistance P.O. Box 4, both with manganin coils |
| 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-8109 |
| 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 4 (EL-SI-8109) | Manganin | ±0.02% to 0.005% | 14 mm thick, rectangular |
| Resistance P.O. Box | Constantan | +0.1% | 12 mm thick, rectangular |
| P.O. Box Ratio Constantan Coil | Constantan | Within ±0.1% | 14 mm thick, rectangular |
Pick the manganin box when the tighter listed accuracy matters, for example in college measurement labs; the constantan boxes cover routine school practicals.
What Is the Resistance P.O. Box 4 Used For?
Like every Post Office box, it is a complete Wheatstone bridge in one case: ratio arms and an adjustable arm whose coils are switched into circuit by withdrawing brass plugs. Students connect a cell, a galvanometer and the unknown resistance, set a ratio, and change the plugged-out coils until the galvanometer reads zero, then multiply the arm value by the ratio to find the unknown resistance or a wire’s specific resistance. Manganin is chosen for its very small change of resistance with temperature and its low thermoelectric emf against copper, which helps keep the DC null steady during a careful measurement. Seat the plugs with a light twist, wipe them clean if readings drift, and never leave a plug half-inserted.
Frequently Asked Questions
What accuracy does this P.O. box have?
The listing gives ±0.02% to 0.005% for the manganin coils. Confirm the accuracy of the version you are quoted with JLab.
What is the difference between P.O. Box 3 and P.O. Box 4?
Both are listed with manganin coils, but the listing does not explain how they differ. Ask JLab for the coil values and layout of each before you choose.
How does it differ from the constantan Resistance P.O. Box?
This box uses manganin coils on 14 mm brass blocks with a tighter listed accuracy; the Resistance P.O. Box uses constantan coils on 12 mm blocks, listed at +0.1%.
Who manufactures it?
Jain Laboratory Instruments Pvt Ltd (JLab) makes the P.O. box at its works in Ambala, Haryana, India.
OEM Manufacturer
JLab is the trading name of Jain Laboratory Instruments Pvt Ltd, a scientific instruments manufacturer in India, incorporated in 2017 and based on Hargolal Road, Ambala, Haryana. The manganin P.O. box comes from JLab’s own works rather than a trader, so colleges, dealers and importers deal directly with the maker, each box is visually inspected, and repeat orders are handled by the manufacturer. JLab exports worldwide and ships to buyers in every region — Taiwan in East Asia, Libya in North Africa, Liberia in West Africa, Sri Lanka in South Asia and the Netherlands in Western Europe, to give a few examples. For tender supply, see the JLab lab tenders page.
Related Bridge Equipment
- Resistance P.O. Box — the constantan-coil P.O. box on 12 mm brass blocks.
- P.O. Box Ratio Constantan Coil — a constantan P.O. box in Ratio 3 and Ratio 4 versions.
- Resistance Box Constantan & Manganin — a dial-switch decade resistance box with manganin or constantan coils.
- Spot Reflecting Galvanometer — a DC null detector for bridges and potentiometers.
- Portable Wheatstone Bridge — a self-contained bridge with built-in galvanometer and battery.
More in the Scientific Instrument range and the Indian Instruments section.
Request a Quote
JLab quotes as the manufacturer. Use the Add To Cart enquiry button on this page, or send the version (Box 3 or Box 4), the quantity (minimum 10 units) and your delivery location through the contact page.
Last updated: 8 October 2026
