Digitise a Bursting Strength Tester: Peak Hold to Wi-Fi Log

A manual bursting strength tester can usually be digitised without replacing the machine.

You add a pressure transducer on the hydraulic line, a controller with a display that shows live pressure and holds the peak at the moment of burst, a peak reset and tare, a field where the operator enters GSM. GSM = grams per square metre (g/m²).

So the bursting factor (BF = bursting strength ÷ GSM, with consistent units) is calculated automatically, a serial (RS-485) output to a printer, and a Wi-Fi log to CSV or Excel. The diaphragm, clamp and pumping mechanism stay as they are, so the test method does not change.

Calibration against a traceable reference is still required before results are used.

Who this is for: quality and lab staff in paper, board and corrugated packaging units who run a dial gauge tester today and want readings that are logged, not written by hand.

How a bursting strength test works

Bursting strength is the hydraulic pressure needed to rupture a sheet clamped over a circular rubber diaphragm. The 1966 edition of IS 1060 Part 1 describes the tester as hydraulic pressure, transmitted through glycerine or compressed air, acting on a pure gum rubber diaphragm in contact with the paper, and it asks that the gauge be chosen so each reading falls between 25% and 75% of the gauge capacity (IS 1060 (Part 1) 1966, public text). Today the bursting strength method for paper is IS 1060 (Part 6/Sec 2):2024, identical to ISO 2758:2014 (Intertek Inform listing for IS 1060 (Part 6/Sec 2):2024). IS 1060 Part 1:2022 (amended October 2025) is a separate part covering general purpose tests. The international methods are ISO 2758:2014 for paper and ISO 2759:2014 for board.

On a manual tester the operator watches a dial with a lazy (maximum) pointer and reads the peak after the sheet bursts. The weak points are reading error, a lazy pointer that sticks or is not reset, and results copied by hand into a register.

Retrofit or buy a new digital machine?

Note the pumping rate. The 1966 IS 1060 text (clause 12.5.2) asks for pressure to rise at about 0.75 kg/cm² per second and does not recommend hand operated hydraulic testers as standard practice. If your manual tester is hand cranked and the rate varies by operator, a display alone will not fix that, and a motorised drive may matter more than the electronics. Check the rate of loading in the current IS 1060 (Part 6/Sec 2) or ISO 2758 text before you decide.

We are not giving cost comparisons in this guide; get quotes for both routes on the same feature list below.

The feature list

Live pressure and peak hold

A pressure transducer on a tee in the hydraulic line replaces, or sits beside, the dial gauge. Size its range so normal bursts fall in the middle of its span; the same 25% to 75% idea from IS 1060 applies. Ask for the transducer’s datasheet accuracy, overload rating and media compatibility with glycerine.

The controller samples pressure fast enough to catch the peak. At burst, pressure drops sharply; the controller must hold the highest value seen. Ask the supplier what sample rate the peak detection uses and how they verified it against a reference gauge. No sample rate figure is stated here because it depends on the hardware chosen.

Peak reset and tare

• Peak reset: a button (or automatic reset on the next pressure rise) clears the held value. A missed reset is the digital version of a stuck lazy pointer, so the log should record the reset event.
• Tare (zero): zeroes the reading with the clamp open and no pressure, removing transducer offset. Do it at the start of each shift and log it.

Bursting factor from GSM

The operator enters the grammage (GSM, g/m² measured per ISO 536) of the lot. The controller computes:

Bursting factor = bursting strength ÷ grammage

Units must match. Common practice is bursting strength in kgf/cm² multiplied by 1000 and divided by GSM, or bursting strength in kPa divided by GSM to give the burst index in kPa·m²/g. ISO 2758 reports burst index as kPa·m²/g. Pick one convention, show the unit on screen and in the log, and do not mix them between reports.

Worked example (illustrative numbers): a board with 150 GSM bursts at 6.0 kgf/cm². 1 kgf/cm² = 98.0665 kPa (by definition of the kilogram-force, NIST SP 811), so 6.0 kgf/cm² = 588.4 kPa. Burst index = 588.4 ÷ 150 = 3.92 kPa·m²/g. Bursting factor in the kgf convention = 6.0 × 1000 ÷ 150 = 40.

RS-485 printer output

Many lab printers accept serial input. RS-485 (TIA/EIA-485) is a differential bus that tolerates long cable runs and plant noise better than single-ended links (TI SLLA272). Agree the print format: date, time, operator, sample ID, GSM, peak, BF, units. If the printer only has RS-232, a converter is needed; ask who supplies it.

Wi-Fi log to CSV or Excel

Each test becomes one row: timestamp, sample ID, operator, GSM, peak pressure, BF, tare and reset events. Ask:

• Where the file lives (on the device, on a PC share, or in a cloud folder)
• What happens if Wi-Fi drops mid shift (local buffer, then sync)
• Whether the file can be edited after the fact (for audit, it should not be, or edits should be logged)
• Whether the export opens directly in Excel without reformatting

Calibration and traceability

A digital display is only as good as its calibration. Ask for calibration of the pressure chain (transducer plus controller) against a reference traceable to national standards; in India that traceability runs to the CSIR National Physical Laboratory (CSIR-NPL), typically through an NABL accredited lab (NABL). Also keep the diaphragm check described in your test standard, since a stiff or worn diaphragm affects results regardless of electronics.

We make no accuracy claim for any retrofit here. Accuracy depends on the transducer, controller, calibration and mechanics, and should be stated on the calibration certificate.

Download the Free “Burst Tester Digitisation Checklist”

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Questions to ask any retrofit supplier

1. Which transducer range and accuracy class, and is it rated for the hydraulic medium?
2. How is peak captured, and how was it verified against a reference?
3. Is tare and peak reset logged?
4. Which BF convention and units are used, and can the GSM be entered per lot?
5. What print format goes to the RS-485 printer?
6. Where is the log stored, what happens when Wi-Fi drops, and is it tamper evident?
7. Who calibrates, against what reference, and how often?
8. Does the retrofit change anything mechanical (pump, clamp, diaphragm)?

Where an HMI controller can fit

If you would rather build the retrofit around a panel HMI than a dedicated indicator, the Em Bose EB series has analog inputs for 4-20 mA or 0-10 V transducers, RS-485 for a serial printer or PC link, and HMI and application logic. Peak hold and bursting factor calculation on it are application and configuration dependent, so they are set up per project, not a standard feature. Embedos does not sell a bursting tester product, and nothing here is a certified test claim.

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