Laboratory Instruments · Laboratory Balances
Mechanical Pan Balance
Mechanical double pan balances in six capacities from 100 g to 5000 g, each supplied with its own weight set and tweezers, reading by lever and rider with no supply, no calibration routine and no data output.
JPT-01 (6 models) ·
Key specifications
- Capacities
- 100 g, 200 g, 500 g, 1000 g, 2000 g and 5000 g across six models
- Readability
- 0.1 g, 0.2 g, 0.5 g, 1 g, 2 g and 5 g by capacity, matching the verification scale interval on every model
- Pan diameter
- 85 mm on the 100 g and 200 g models, then 115 mm, 140 mm, 170 mm and 205 mm as capacity rises
- Method
- Lever and Roberval mechanism with external weights and a sliding rider; no electronics, no supply and no calibration routine
- Weights supplied
- A weight set and one pair of tweezers with every model, five to eight weights depending on capacity
- Beam scale
- Printed rider scale divided to 5 g, read against the pointer
- Construction
- Light alloy frame on a metal base finished in electrostatically applied paint, with moulded pans as standard
- Pan option
- Stainless steel pans are available and differ from the standard pans only in material
- Dimensions
- 200 x 70 x 150 mm for 100 g and 200 g, rising to 300 x 80 x 175 mm for 1000 g
- Output
- None. The balance has no display, no interface and no power connection
A double pan mechanical balance is the oldest kind of weighing instrument still in daily use, and it works on a principle that has never needed replacing: put the sample on one pan, put known weights on the other, and let the beam tell you when the two agree. There is no sensor, no supply and nothing to calibrate. The reading is the sum of the weights on the pan and the position of a rider on a graduated beam.
This range covers six capacities from 100 g to 5000 g, each with its own weight set and tweezers, in a moulded pan or a stainless steel one. It is worth being direct about what it is, because the phrase laboratory balance is now used mostly for electronic instruments with an entirely different construction. This is the mechanical kind, and the differences matter at the point of ordering rather than afterwards.
What this balance is, and what it is not
An electronic balance suspends the pan on an electromagnetic force compensation cell, measures the current needed to hold it, adjusts itself against an internal reference mass and can send the result to a printer or a computer. This balance has none of that. It compares the sample against external weights placed on the other pan by an operator, reads through a lever and a pointer, and has no supply, no self-adjustment and no interface of any kind.
That is a set of limitations and a set of advantages, and both are real. There is no warm-up, no calibration routine to keep up with, no drift, no battery and nothing to configure; the balance works on a bench with no power and it can be understood completely by looking at it. Against that, it cannot report a value finer than its readability, it cannot record or transmit a result, and a reading between two divisions has to be estimated by eye.
The practical consequence is that where a result has to be recorded automatically, traceable to a certificate, or read below 0.1 g, an electronic balance is the instrument and this one is not a substitute for it. Where a sample simply has to be weighed accurately to a tenth of a gram or a gram, on a bench, with nothing to set up, this is a simpler instrument doing a job that has not changed.
How the balance works
The beam is carried on knife edges, and a Roberval mechanism keeps each pan level as the beam moves, so that the sample sits over the same point regardless of where on the pan it is placed. That last part matters more than it sounds: without the parallel linkage, a weight placed near the edge of a pan would exert a different turning moment from the same weight at the centre, and the reading would depend on how the sample was arranged. The mechanism removes that dependence.
The mass of the sample is then the sum of two quantities. Weights are added to the right pan, from the largest down, until the pointer is close to its mark; the rider is then slid along the graduated beam until the pointer sits exactly at the mark. The value the rider indicates is added to the weights already on the pan. The beam scale is divided to 5 g, and the beam itself is set level before any weighing, with the rider at zero and both pans empty, by turning the balance nut until the pointer rests on the centre line.
Choosing a capacity
The capacity and the readability move in opposite directions, and the choice follows from the smallest sample rather than the largest. The 100 g model reads to 0.1 g; the 5000 g model reads to 5 g. A fine readability on a large capacity is not available here, because the resolution is set by the beam, the rider scale and the pointer rather than by an electronic display.
A second figure follows the capacity: the pan. It runs from 85 mm on the 100 g and 200 g models to 205 mm on the 5000 g model, and the body grows with it. Where a bulky container has to stand on the pan, that matters as much as the capacity does, because a pan that is too small for the container forces the sample to be transferred.
The material treats the 100 g, 200 g, 500 g and 1000 g capacities as the standard ones and gives their dimensions and weight sets in full. The 2000 g and 5000 g models appear in the parameter table with their pan sizes and readabilities, but without a body dimension and with the weight set described differently. Those two should be confirmed at the enquiry rather than read off the standard data.
The weight set and the rider scale
Every model is supplied with a weight set and one pair of tweezers in a box. The set for the 100 g model is five weights, rising to seven or eight for the 1000 g model, and the composition is listed for each of the four standard capacities on this page. It is worth understanding how the set and the rider work together: the weights bring the balance close to the sample mass, and the rider, which reads to 5 g, supplies the remainder. That is why a set does not need to contain every mass, and why the same set serves a range of samples.
The composition the material gives for the 2000 g and 5000 g models is expressed as a count against each weight mass rather than as a list, and the two tables in the material do not reconcile exactly. Nothing has been calculated here to make them agree. For those two capacities the contents of the box should be confirmed when ordering, and the same applies if the exact set matters for a specific range of samples.
Setting up and using the balance
Set the balance on a flat, level bench. It has no levelling feet, so it relies on the surface underneath it, and a bench that is not level will show as a pointer that will not centre. Remove the protective sleeves from the mechanism and the pointer, slide the rider to the zero mark at the left of the beam, and turn the balance nut until the pointer rests on the centre line of the divided plate with both pans empty. The beam is now level and the balance is ready.
Weigh by placing the sample on the left pan and adding weights to the right pan with the tweezers, starting from the largest and working down. Keep both the sample and the weights towards the centre of their pans. When the remaining difference is smaller than the smallest weight available, slide the rider until the pointer centres and add the rider value to the weights on the pan. When the weighing is finished, return the rider to zero and put the weights back in the box.
Care and storage
The weights are the part of the set that degrades, and the reason is handling. Skin oil, moisture and abrasion all change the mass of a weight, so the tweezers supplied are not a convenience but part of the measurement: weights are lifted with them and never with the fingers. Keep the balance and the weights dry and away from acid, alkali, oil and grease, brush them clean with a soft brush before and after use, and return the weights to the box rather than leaving them on the bench.
The material advises that a balance or a weight that has been damaged, has corroded, or is of doubtful mass should be checked before it is used again rather than compensated for by adjusting the balance. Where a laboratory needs the weighing to be traceable, that is a separate question: the material does not state whether a calibration certificate or a traceable weight certificate is available, and it gives no type approval for trade or regulated weighing, so both are raised at the enquiry rather than assumed.
Ordering
The items that decide the answer are the smallest and largest masses to be weighed and the accuracy required at the small end, which together fix the capacity and the readability, the size of the container that has to stand on the pan, whether the samples are wet or staining enough to need the stainless steel pan, whether the weighing has to be recorded or traceable, and how many balances are needed. Quantity, destination port and required delivery date complete the enquiry.
Features
- Six capacities from a single pattern, so a laboratory can standardise on one balance it already knows across a range of sample sizes
- A weight set and tweezers with every model, so nothing further has to be bought before the balance can be used
- No supply, no warm-up and no calibration routine, which is what makes it usable on a bench with no power and in teaching rooms where simplicity is the point
- A stainless steel pan option where the sample is wet, acidic or likely to stain a moulded pan
- A frame designed to resist deformation, which matters because the reading depends on the mechanism holding its geometry
- A readable beam scale divided to 5 g, which is enough resolution for a sample weighed to the readability of the model
Technical specifications
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
| JPT-01 | 100 g capacity, 0.1 g readability, 85 mm panStandard |
|---|---|
| JPT-02 | 200 g capacity, 0.2 g readability, 85 mm panStandard |
| JPT-05 | 500 g capacity, 0.5 g readability, 115 mm panStandard |
| JPT-1 | 1000 g capacity, 1 g readability, 140 mm panStandard |
| JPT-2 | 2000 g capacity, 2 g readability, 170 mm panStandard |
| JPT-5 | 5000 g capacity, 5 g readability, 205 mm panStandard |
| Verification scale interval | Equal to the readability on every model, as listedStandard |
| Weighing principle | The mass of the sample equals the mass of the weights plus the mass the rider scale indicatesStandard |
| Fine reading below the readability | Not available. A mass between two divisions has to be interpolated by eye against the pointerStandard |
| With 100 g, five weights | 5 g x 1, 10 g x 1, 20 g x 2, 50 g x 1, with one pair of tweezersStandard |
|---|---|
| With 200 g, six weights | 5 g x 1, 10 g x 1, 20 g x 2, 50 g x 1, 100 g x 1, with one pair of tweezersStandard |
| With 500 g, seven weights | 10 g x 1, 20 g x 2, 50 g x 1, 100 g x 2, 200 g x 1, with one pair of tweezersStandard |
| With 1000 g, seven to eight weights | 10 g x 1, 20 g x 2, 50 g x 1, 100 g x 2, 200 g x 1, 500 g x 1, with one pair of tweezersStandard |
| With 2000 g and 5000 g | Listed in the material as a count against each weight mass rather than as a list, and the set for those two capacities should be confirmed against the delivered weight boxInformation required |
| Reconciliation of the set | The composition list and the count table in the material do not agree exactly, and the totals were not derived here; confirm the set per capacity before orderingInformation required |
| Weight box | Supplied as a boxed setStandard |
| Frame | Light alloy, described as resistant to deformation and rustStandard |
|---|---|
| Base | Metal base with an electrostatically applied paint finishStandard |
| Pans | Moulded plastic as standard; stainless steel available as an upgrade that differs only in the pan materialStandard |
| Beam and scale | Printed scale with a sliding rider and a pointer against a divided plateStandard |
| Components | Nameplate, pointer, centre knife edge, pans, pan carriers, scale, rider, limit bracket, balance screw, balance nut, beam, side knife edges and baseStandard |
| Dimensions | 200 x 70 x 150 mm for 100 g and 200 g; 255 x 75 x 175 mm for 500 g; 300 x 80 x 175 mm for 1000 gStandard |
| Dimensions for 2000 g and 5000 g | Information requiredInformation required |
| Net weight | Information requiredInformation required |
| Supply | None required; the balance is entirely mechanicalStandard |
|---|---|
| Calibration routine | None. The beam is set level once with the balance nut and checked by eye against the pointerStandard |
| Working surface | A flat, level bench; the balance has no levelling feet and relies on the surface it stands onStandard |
| Storage | Keep dry and free of acid, alkali, oil and grease; clean with a soft brush before and after use and return the weights to the boxStandard |
| Handling of weights | Weights are lifted with the tweezers supplied and never with the fingersStandard |
| Calibration certificate | Information requiredInformation required |
| Type approval for a regulated or trade purpose | Information requiredInformation required |
Available models
| Model | Configuration | Key ranges | Availability |
|---|---|---|---|
| JPT-01 | 100 g capacity, 0.1 g readability, 85 mm pan | Five weights supplied: 5 g, 10 g, 20 g x 2 and 50 g | The finest readability in the range and one of the four capacities the material treats as standard. Body 200 x 70 x 150 mm |
| JPT-02 | 200 g capacity, 0.2 g readability, 85 mm pan | Six weights supplied: 5 g, 10 g, 20 g x 2, 50 g and 100 g | Same body size and pan as JPT-01, with the capacity raised to 200 g at 0.2 g readability |
| JPT-05 | 500 g capacity, 0.5 g readability, 115 mm pan | Seven weights supplied: 10 g, 20 g x 2, 50 g, 100 g x 2 and 200 g | Body 255 x 75 x 175 mm, with the larger pan that the added capacity needs |
| JPT-1 | 1000 g capacity, 1 g readability, 140 mm pan | Seven to eight weights supplied: up to 10 g, 20 g x 2, 50 g, 100 g x 2, 200 g and 500 g | The heaviest of the four capacities the material presents as standard. Body 300 x 80 x 175 mm |
| JPT-2 | 2000 g capacity, 2 g readability, 170 mm pan | Weight set given as a count against each mass; confirm before ordering | Listed in the parameter table without a body dimension |
| JPT-5 | 5000 g capacity, 5 g readability, 205 mm pan | Weight set given as a count against each mass; confirm before ordering | The largest capacity in the range. Listed without a body dimension |
Customization
- Pan material selected between the moulded pan and the stainless steel pan, which differ only in the material of the pan
- Capacity selected from the six sizes listed
Certification and compliance
Certification documents not yet supplied
Certifications are only published once a certificate copy can be produced, so this section is deliberately empty rather than populated with assumed approvals. Tell us which approvals your application requires and we will confirm what is available for this instrument.
Parameters still to be confirmed
The following are required for a complete specification but are not stated in the documentation supplied to us. They are listed rather than estimated:
- Body dimensions for the 2000 g and 5000 g models, which the material lists without a dimension
- The exact contents of the weight box for the 2000 g and 5000 g models, since the material gives those as counts against each mass rather than as a list
- Net weight of each model, and the packed weight and box dimensions for freight calculation
- Whether a calibration certificate or a traceable weight certificate is available
- Whether the instrument or its weight set holds any type approval for a trade or regulated weighing purpose
- The model numbers to which the stainless steel pan applies, since the material states the option without giving the corresponding codes
- Whether replacement weights, pans or tweezers can be supplied separately
- Body material of the plastic pan and whether it is suitable for food contact
- Warranty period and the terms that apply
- English-language datasheet and an assembly or parts diagram
Frequently asked questions
Is this the same kind of instrument as an electronic laboratory balance?
No, and the difference is worth being clear about before ordering. An electronic balance suspends the pan on an electromagnetic force compensation cell, corrects itself against an internal reference mass, and can output the reading. This balance compares the sample against external weights placed on the other pan by an operator: it has no sensor, no supply, no self-adjustment and no interface. What it does have is simplicity, independence from power and a reading the operator can see being established. Where the requirement is a reading finer than 0.1 g, a result that has to be recorded automatically, or a documented calibration, an electronic balance is the instrument and this one is not a substitute for it.
How do I read a mass on it?
The mass is the sum of two things. The weights on the right pan are added up, and the rider position on the beam scale supplies the remainder up to 5 g. So a sample is balanced by adding weights from the largest downwards with the tweezers until the pointer is close, then sliding the rider until the pointer sits at the mark, and adding the rider value to the weights already on the pan. The balance has to be set level first by sliding the rider to zero and turning the balance nut until the pointer rests at the centre mark with both pans empty.
Can it weigh something outside the reading of the model I have?
Not below the readability of the model. A 0.5 g readability model cannot report a difference smaller than 0.5 g, and a value between two divisions has to be interpolated by eye against the pointer, which is an estimate rather than a measurement. Where the samples are small, the capacity and the readability have to be chosen together: the finer the readability in this range, the lower the capacity, which is why the 100 g model reads to 0.1 g while the 5000 g model reads only to 5 g. Choose the model around the smallest sample that has to be weighed, not the largest.
Why does the material give two different descriptions of the weight set?
Because the two tables describe the sets in different ways and their figures do not reconcile exactly. One table lists the composition for the four main capacities as a set of weights for each, while the second gives a count against each weight mass across all six capacities and leaves some cells unmarked. Nothing was calculated here to make the two agree. The composition for the four main capacities is published as the first table gives it, the two largest capacities are listed as requiring confirmation, and the exact contents of the box should be checked when ordering.
What does it need in the way of maintenance?
Very little, and most of it is about the weights rather than the balance. Keep the balance and the weights dry and away from acid, alkali, oil and grease; brush them clean with a soft brush before and after use; lift the weights with the tweezers and never with the fingers, because skin oil changes their mass over time; and return the weights to the box and slide the rider back to zero when the weighing is finished. The material advises that a balance or weight that is damaged, corroded or of doubtful mass should be checked before it is used again.
Request a quotation for the JPT-01
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Request a quotation - JPT-01
Send the technical detail and we will confirm availability, lead time and terms. In-stock items ship within 48 hours; customized specifications typically take 2-10 days. Minimum order quantity is 1 pc.