PISONICS
PS7110 Series
Inline Process Refractometer
Critical angle · thin-layer interface · indifferent to colour and turbidity
Inline Brix monitoring in sugar refining and brewing
— Sugar liquor · glucose · brewing process concentration —
Measured: Brix / refractive index nD
Inline Brix monitoring in sugar refining and brewing
Process background
Almost every stage in sugar and brewing controls the same quantity: total dissolved solids, which the industry expresses as Brix. From thin juice through evaporation and concentration, to judging supersaturation before crystallisation, to syrup blending and tracking gravity through fermentation — every step is asking how much is in solution right now.
That is refractometry's home ground: refractive index and total dissolved solids follow one stable single-valued curve. And the liquids on this line are typically dark, cloudy and carrying bubbles — caramelised syrup, yeast-laden wash, juice bases with suspended solids. Transmission instruments distort on those. Critical-angle refractometry does not, because the light was never going to pass through them.
What the method can and cannot do here
What it can do:
- Total dissolved solids as Brix — 0–90 %Brix on the A variant, 0–100 %Brix on B and C
- Dark, cloudy, bubbly liquids — none of it affects the reading
- Direct traceability against a laboratory refractometer — the same physical quantity, so plant and lab agree
What it cannot — stated here so nobody specifies it into the wrong duty:
- Separating two components that move the index the same way — a sugar-plus-alcohol system needs the PS7100 spectroscopic route
- Suspended solids content — refractometry reads what is dissolved, not what is suspended
- Staying accurate through filming, sugar deposit or crystallisation — those duties need a cleaning unit, see below
Selecting the PS7110
| Variant | Prism | Process temp. | RI range | Suits |
|---|---|---|---|---|
| PS7110-A | High-strength optical glass | 0 – 60 °C | 1.33299 – 1.51782 | Ambient, non-abrasive, span within 0–90 %Brix |
| PS7110-B | Sapphire | 0 – 70 °C | 1.33299 – 1.57041 | The default for most inline duties; 0–100 %Brix |
| PS7110-C | Sapphire | −10 – 100 °C | 1.33299 – 1.57041 | Evaporation and concentration duties; the −10 °C floor also covers cold-side points |
A sanitary installation is straightforward: the PS7110-MT4 sanitary adapter or a compact tri-clamp for the connection, CIP and SIP for cleaning, with a cleaning temperature range of −30 to 120 °C.
The variant is chosen mainly on temperature: ambient blending and fermentation tracking are fine on the A, while evaporation and concentration go to the C (−10 to 100 °C). Points where saturated sugar solution can crystallise should carry the PS7110-CL2 high-pressure flushing unit; syrups that film take the PS7110-CL1 ultrasonic unit.
General specification:
| Item | Specification |
|---|---|
| Measured quantity | Refractive index nD, converted to concentration through a scale (%Brix or wt% / vol%) |
| Accuracy | Concentration ±0.1 %; refractive index ±0.0001; temperature ±0.5 °C |
| Resolution | Concentration 0.01 %; refractive index 0.00001; temperature 0.1 °C |
| Pressure | ≤ 1.5 MPa at the prism face |
| Cleaning temperature | −30 – 120 °C; CIP and SIP capable |
| Wetted materials | SS316L plus prism; B / C accept PTFE / Hastelloy / titanium / tantalum |
| Outputs | 4–20 mA / RS485 / RS232 / USB |
| Hazardous area | Ex ia IIC T6 Ga (intrinsically safe) |
The scale has to be built for your medium
This is the most commonly misunderstood thing about refractometry, so it goes near the front.
What is calibrated at the factory is refractive index and temperature, unit by unit in standard units. That part is independent of the medium, so several instruments agree with one another. The concentration scale, however, belongs to the medium — the curve from index to concentration is a property of one liquid, and a scale built for one medium cannot be used for another.
In practice that is three things. One: tell us the medium and you get the matching scale. Two: a change of recipe, product or process stage means a change of scale, but not a trip back to the factory — RI verification, self-service modelling from sampled laboratory values and multi-point temperature compensation are all done on site. Three: be careful with multi-component systems — the same refractive index does not mean the same concentration. Two components that move the index the same way cannot be separated by refractometry, and that duty belongs to the PS7100 spectroscopic route.
Installation and upkeep
Refractometry reads a thin layer of liquid at the prism face, so a trustworthy reading rests on two things only: whether the face is always washed by liquid that represents the process, and whether it is clean.
- The face must never point downward — a downward face collects deposit, and deposit raises no fault; it shows up only as a slow one-way drift
- In a vertical line the flow must run upward — a downward run drains when the pump stops, the prism is left uncovered, and the reading stops meaning anything
- On a horizontal line, entry from below (face up) or from the side (face vertical) are both fine; entry from the top is not permitted
- Four mounting schemes: valved bypass (recommended — service it without stopping the main line) / direct in-line (cheapest, service needs a shutdown) / pumped tank loop (steadiest conditions) / tank wall (simplest)
- 2″ and under takes the PS7110-MT1 small-bore adapter; where the face has to be inspected visually, the MT2 / MT3 tee and cross carry sight glasses
- Media that can carry grit or abrasive particles must be filtered upstream — the detection window is a wear part
The cleaning strategy belongs in the design, not in a response to a reading that has already drifted: sanitary processes use CIP and SIP directly; media that coat or film take the PS7110-CL1 ultrasonic unit for continuous cleaning; media that crystallise or deposit particles take the PS7110-CL2 high-pressure flushing unit on a timed cycle.
The instrument carries prism condition diagnostics: the position of the shadow line is the measurement, and its sharpness and contrast are a second quantity the same detector sees at the same time. A deposit blunts the edge before it shifts the position, so the instrument reports its condition before the reading is visibly wrong rather than quietly returning a plausible number. It does not replace looking at the face, though — putting that into the routine inspection is worth more than any coefficient correction applied afterwards.
Before you order
These are what decide the variant, the accessories and the scale. Sending them over is quicker than guessing from a datasheet.
- Medium and process stage (thin juice / concentrated syrup / glucose / wort / wash…) — this sets the scale
- Working concentration band and the control tolerance you actually need
- Process temperature range including startup and cleaning — this picks A / B / C
- Pipe size or vessel connection — this picks tri-clamp / MT1 / MT4
- Whether the medium crystallises or films — this decides CL1 / CL2 versus CIP alone
- Whether you want the scale modelled from your own laboratory data (we can do it on site)
This page is a method and selection note, not a case study. The PS7110 has no publicly citable installed base in this industry yet, so there are no unit counts, saving percentages or payback periods here — we do not invent those. Give us the process conditions and you get a selection opinion you can check, which is worth more than a handsome case study.
In closing
The Pisonics PS7 range covers several measuring principles: acoustic impedance (PS7000), acoustic attenuation (PS7010), sound velocity (PS7020), spectroscopy (PS7100), refractometry (PS7110), Coriolis (PS7200), differential pressure (PS7300), tuning fork (PS7400) and microwave (PS7600). Different principles see different things, and selection always starts with what the duty actually needs measured.
The PS7110 series takes the critical-angle route: the measurement happens in a thin layer at the prism face, which is why colour, turbidity and bubbles do not interfere — and why the prism face has to be kept clean. Sugar and brewing liquids sit squarely on its good side: dissolved-solids concentration, dark and cloudy, sanitary connections.
For a non-standard span, special wetted materials, a hazardous-area version, or to have us build the concentration scale from your own sampled laboratory data, please get in touch with our engineering team.
