P.O. Box Ratio Manganin Coil Manufacturer,Supplier and Exporter in India
Product Code : EL-SI-8135
Jlab Export is a leading P.O. Box Ratio Manganin Coil Manufacturer,and suppliers in India
P.O. Box Ratio Manganin Coil (code EL-SI-8135) is a Post Office box–type resistance box with manganin coils, for Wheatstone bridge resistance measurements where a closer coil tolerance is wanted in college and school physics labs. The coils are listed at ±0.02% to 0.005% and are mounted on 14 mm thick rectangular brass blocks, in Ratio 3 and Ratio 4 versions. It is made by Jain Laboratory Instruments Pvt Ltd (JLab) at its works in Ambala, India.
Specifications
| Parameter | Detail |
|---|---|
| Coil wire | Manganin |
| Accuracy | ±0.02% to 0.005% (as listed) |
| Blocks | Rectangular brass blocks, 14 mm thick |
| Versions listed | P.O. Box Ratio 3 (Manganin Coil) and P.O. Box Ratio 4 (Manganin Coil) |
| Quality check | Each 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-8135 |
| 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 box (EL-SI-8135) | Manganin | ±0.02% to 0.005% | 14 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% | 14 mm thick, rectangular |
Choose manganin over constantan for tighter coil values. The Resistance P.O. Box 4 listing shows the same wire, accuracy and blocks; ask JLab which layout suits you.
What Is the Manganin P.O. Box Used For?
A Post Office box packs a Wheatstone bridge into one case of plug-in coils; with a cell, a galvanometer and two tapping keys it finds an unknown resistance by adjusting the arms until the galvanometer shows no deflection. Manganin, a copper–manganese–nickel alloy, is the usual wire for precision resistors because its resistance hardly changes with temperature or with time, and it develops very little thermoelectric emf where it meets copper or brass. Clean the plugs, seat them firmly with a slight twist, and close the battery key before the galvanometer key.
Frequently Asked Questions
What accuracy are the manganin coils?
The listing gives ±0.02% to 0.005%. Ask JLab which figure applies to which coils in the version you order.
Which versions are available?
P.O. Box Ratio 3 and P.O. Box Ratio 4, both with manganin coils and 14 mm rectangular brass blocks. Coil values are not stated in the listing, so confirm them with JLab.
Why choose manganin instead of constantan?
Both alloys change little with temperature, but manganin is the standard choice for precision resistors and this box is listed at a closer tolerance than the constantan version (within ±0.1%).
Who manufactures it?
JLab (Jain Laboratory Instruments Pvt Ltd) winds and assembles the box at its works in Ambala, Haryana, India.
OEM Manufacturer
JLab is the trading name of Jain Laboratory Instruments Pvt Ltd, an Indian manufacturer of physics and electrical lab instruments, incorporated in 2017 and based on Hargolal Road, Ambala, Haryana. This P.O. box comes from JLab’s own works rather than a trader, so schools, colleges, dealers and importers order it from the maker, and each box is visually inspected before it is packed. JLab exports worldwide and ships to buyers in every region, such as North Macedonia in Southern Europe, Belize in Central America and the Caribbean, Luxembourg in Western Europe, Poland in Eastern Europe and Bangladesh in South Asia. See the JLab lab tenders page for tender supply.
Related Bridge Equipment
- P.O. Box Ratio Constantan Coil — the constantan-coil version for routine teaching.
- Resistance P.O. Box 4 — a manganin-coil P.O. box with 14 mm brass blocks.
- Standard Resistance — aged manganin coils in oil-filled metal vessels.
- Galvanometer — null detector for bridge practicals.
- Tapping Key — momentary-contact keys for the cell and galvanometer circuits.
More items are in the Scientific Instrument range and the Indian Instruments section.
Request a Quote
JLab quotes directly as the manufacturer. Use the Add To Cart enquiry button, or send the version (Ratio 3 or Ratio 4), the quantity (minimum 10 units) and the delivery location through the contact page.
Last updated: 8 October 2026
