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Quality Instrumentation for the Life Sciences

CIRAS-4 Elevating the high-level field research experience

CIRAS-4 Portable Photosynthesis System

Don’t let its compact size fool you.

The highly accurate CIRAS-4 Portable Photosynthesis System is a lightning-fast portable powerhouse that will elevate your research experience.

Its advanced software is exceptionally intuitive and customizable. You can manage environmental controls—as well as how you view your data—all from the touchscreen.

It’s so easy to use, you can begin taking measurements right out of the box.

An exceptional user experience

Minimal Size. Maximum Performance.

The CIRAS-4 is designed with the high-level field researcher in mind. Its small size makes it the most portable photosynthesis system of its kind, alleviating the need for assistance or tripods.

The innovative design of the CIRAS-4 utilizes its small system volume to ensure faster equilibration as well as the most rapid and accurate measurements available. Faster measurements allow the user to expand the parameters of their research and use their time and resources efficiently. Check out the size and weight of the CIRAS-4 console and leaf cuvettes and you will quickly discover why smaller and lighter is better.

high contrast touchscreen

The CIRAS-4’s full-color touch display offers fast-response touch navigation for all system operations. Exceptionally bright LEDs are adjustable for sunlight readability in any condition.


Packed with power.

CIRAS4 Battery StatusThe CIRAS-4 comes standard with three (3) rechargeable Li-ion battery packs that provide 16+ hours of continuous operation. All 3 batteries can charge simultaneously allowing the user to collect lots of data without the interruption of swapping out battery packs. 

Fast response. Fully mobile.

The location of the CIRAS-4’s IRGAs (Infrared Gas Analyzers) in the main console — right next to the internal gas mixing system and flow control — allows the CIRAS-4 to provide an ultra-fast response to changes in “reference” gas, and the fastest and most accurate portable photosynthesis measurement available. IRGAs in the console makes the entire system highly portable, not to mention the added protection from dirt, dust, and debris commonly found in and around a leaf cuvette.

CIRAS-4 Portable Photosynthesis System

True differential analyzer for the ultimate accuracy & reliability.

The heart and soul of any photosynthesis system is the analyzer. Accurate, reliable, and stable measurement and control of CO2 and H2O are critical for high-level research. A “true differential analyzer”, the CIRAS-4 features 4 independent, non-dispersive gas analyzers for accurate, simultaneous measurement and control of both CO2 and H2O — a significant advantage over “gas switching” systems and a major requirement for most researchers. The analyzers act as absorptiometers measuring infrared absorption only. The temperature-controlled optical bench is pressure compensated ensuring the most accurate measurement of CO2 and H2O under changing ambient conditions.

No factory recalibration required

Expect nothing less than the most accurate, reliable, and stable calibration of CO2 and H2O for many years without the need for inconvenient, time-consuming, and costly return-to-factory calibration. Our innovative, proprietary Auto-Zero measurement technique ensures inherent calibration stability confirmed by more than 35 years of experience in gas analysis technology. It allows for very fast warm-up, quick adaptation to changing ambient conditions, and excellent long-term stability. Auto-Zero also minimizes effects on span gas sensitivity, IR source aging, and changes in detector sensitivity and electronics. Simple, periodic system checks are recommended to confirm system integrity and calibration.

Full environmental control:
Automated. Programmable. Standard.

The level of environmental control in the field with the CIRAS-4 is unsurpassed.  The CIRAS-4 offers complete, independent, and automatic control of CO2, H2O, temperature, and light for response curves (i.e. A/Ci curves, light response, etc.) with fast time response.  Control over all environmental parameters can be dynamic or pre-programmed for automated response curve generation.  All power required for environmental control is provided by the internal rechargeable Li-ion batteries (no external power supply is required).

CO2 Control

Unlike some systems, automatic CO2 control is standard with the CIRAS-4.  Automatic and programmable CO2 control is standard with the CIRAS-4. PP Systems pioneered the method of controlling CO2 back in 1992 (CIRAS-1) using mini CO2 cartridges that are commercially available and easily sourced worldwide. Our proprietary gas mixing technology and CO2 regulator provide an accurate, stable, and constant flow of CO2. Each CO2 cartridge provides at least 12 hours of continuous use in the field and our CO2 regulator and cartridge holder are maintenance free. If required, the CIRAS-4 can easily be connected to an external CO2 source as well as programmed and configured for ambient CO2 measurements.

Measurement Range: 0 – 10000 µmol mol-1
Control Range: 0 – 2000 µmol mol-1
set your environmental controls
CIRAS-4 CO2 & H2O Control Screen

H2O Control

PP Systems also pioneered the method of controlling H2O automatically. Programmable H2O control is standard on the CIRAS-4. Onboard, self-conditioning desiccants are used for controlling H2O via user-defined settings. The CIRAS-4 can control H2O based on a percentage of ambient, VPD (Vapor Pressure Deficit), or a specific H2O concentration. The CIRAS-4 can easily be programmed for H2O measurements above and below ambient, and can also be configured for ambient H2O measurements.

Measurement Range: 0 – 75 mmol m-1
Control Range: 0 – Dewpoint

See how quick and easy it is to set and adjust CO2, H2O, temperature, light, and flow rate on the CIRAS-4 Portable Photosynthesis System.

Temperature Control

The CIRAS-4 features the widest range, as well as the fastest and most reliable temperature control in the industry. Each leaf cuvette’s integral automatic temperature control is highly accurate and stable. Peltier coolers with heat sink and fan are mounted on all cuvette heads for precise control over a wide range of temperatures. The CIRAS-4 can be programmed to control to a specific leaf temperature, a specific cuvette air temperature or to track leaf to ambient. Temperature control can also be disabled.

Temperature Control Range:  12 oC below ambient to 15 oC above ambient
Ambient Temperature Limits:  0-45 oC
full control of temperature
CIRAS-4 Temperature Control Screen

Light Control (Optional)

Automatic control of light intensity is achieved with our compact, low-power lightweight LED (RGBW-FR) light units available for each of our PLC4 Leaf Cuvettes.

Measurement Range: 0 – 3000 µmol m-2 s-1
Control Range: 0 – 2500 µmol m-2 s-1

Each light unit features a bank of red, green, blue, and white LEDs as well as far-red LEDs to allow users control of up to 30% of PFD light intensity. In addition to controlling light intensity, you can also control the proportion of light by wavelength, which can be especially useful for research on plant responses to different wavelengths.

Full control of light

Test the benefits of CIRAS-4’s small system volume

Small System Volume: Proven to be faster & more accurate

When evaluating the different types of portable photosynthesis systems on the market, it’s very important to consider not only size and portability, but system volume as well. Size and chamber volume are critically important when it comes to rapid, accurate measurement of leaf gas exchange. The CIRAS-4 Portable Photosynthesis System’s small system volume ensures faster equilibration time resulting in the most rapid and accurate measurements available. These simulators will help to illustrate why.

Dilution Model:

This model illustrates the fundamental process of exponential dilution, in which flow rate and volume are the only variables that really matter. Select the Dilution Model tab and use the sliders to adjust the parameters. Calculate to watch the concentrations change in real time. 

As you will clearly see, chambers with smaller system volume have fundamental speed advantages over chambers with large volume. 

CIRAS-4 Model:

Based on the CIRAS-4 Portable Photosynthesis System including our PLC4 Universal Leaf Cuvette, this model demonstrates the transport time to move analysis (sample) gas back to the CIRAS-4 console. Also shown for comparison purposes is a typical IRGA-in-the-head system with much larger cuvette volume (~ 80 – 140 cc).

PLC4 Leaf Cuvettes

Slide background
Lightweight. Fast. Precise.
• Head plates secured with magnets - no tools needed!
• Automatic temperature control
• Airtight seal without damage to vegetation
• Fastest response to CO2 and H2O changes
• Optional LED Light Unit (RGBW-FR)
• Minimal boundary layer resistance
PLC4 Universal Leaf Cuvette shown.
PLC4 Universal Leaf Cuvette

No tools required.

Head plates are secured in place by magnets for quick and easy change out in the lab or field.

Rulers on apertures.

Rulers are available on larger head plates to assist with better leaf area approximation.

PLC4 Leaf Cuvette Rulers
Changing head plates is quick and easy

Minimal boundary layer resistance.

Advanced air mixing inside the chamber reduces boundary layer resistance.

Temperature control

All PLC4 Leaf Cuvettes offer a temperature control range of approximately 12°C below ambient up to 15°C above ambient with 0.1°C precision.

Easy and accurate leak diagnosis.

Direct pressure measurement inside the cuvette for easy and accurate leak diagnosis.

PLC4 Universal Leaf Cuvette

The PLC4 Universal Leaf Cuvette comes with three interchangeable head plates and is compatible with the CFM-4 Chlorophyll Fluorescence Module for simultaneous measurement of leaf gas exchange and chlorophyll fluorescence.

25 mm x 18 mm
25 mm x 7 mm
18 mm diameter

PLC4 Broad/Narrow/Conifer Leaf Cuvette

Broad: 30 mm x 30 mm

The PLC4 Broad/Narrow/Conifer Leaf Cuvette comes with three interchangeable heads for measurement on large, flat broad leaves, narrow leaves, and grasses and conifers. 

Narrow: 86 mm x 37 mm
Conifer: 76 mm x 36 mm

PLC4 LED Light Units (RGBW-FR)

PLC4 LED Light Unit

Automatic control.

Optional light units are available for automatic control of light for all PLC4 leaf cuvettes. Each light unit features a bank of red, green, blue, and white LEDs, allowing for automatic control of both light intensity up to 2500 μmol m-2 s-1 and proportion (%) of light by wavelength. All light units are designed to ensure uniform light distribution over the entire leaf area for accurate results.

PLC4 Universal LED Light Unit


Our PLC4 LED light units are the only cuvette light units available with 4 far-red LEDs (730 nm +/- 5 nm). CIRAS-4 users will be able to control far-red up to 30% of Photon Flux Density (PFD), allowing for more accurate recreation of natural light.

Wavelength (RGBW-FR)

Color Peak Full Width at Half Max
Red 660 nm ± 10 nm 20 nm
Green 527 nm ± 7 nm 38 nm
Blue 447 nm ± 7 nm 18 nm
White 400 – 730 nm
Far-red 730 nm ± 10 nm 32 nm
Light Control Range: 0 – 2500 µmol m-2 s-1

Why is far-red important?

Far-red (700-750 nm) is about 18% of the photon flux in sunlight, and far-red makes up an even more significant fraction of the photon flux in understory conditions. Recent research has shown that this far-red light is photosynthetically active. Taking photosynthesis measurements with a light spectrum that does not include far-red (e.g., white or red/green/blue LEDs) will result in lower photosynthetic rates compared to photosynthetic rates under sunlight (with the same PFD). Being able to control the amount of far-red light during photosynthesis measurements will more accurately mimic rates under sunlight or understory conditions.  CIRAS-4 users can control far-red up to 30% of Photon Flux Density (PFD), allowing users to recreate the natural light environment more accurately.

Is PAR really 400-700 nm? The McCree Curve revisited with evidence ePAR should be the new standard.

Dr. Bruce Bugbee breaks down the latest evidence that the officially recognized PAR (aka PPFD) range of 400-700 nm should be revised to include far-red photons up to 750 nm. The traditional photosynthetically active radiation range was defined based on research by Dr. Keith McCree and other scientists and has been the standard for measuring plant lighting efficacy for over 50 years. Should the new “ePAR” (extended PAR) range become the new standard? Check out the newest evidence and implications presented in this video and judge for yourself.

Simultaneously measure photosynthesis & chlorophyll fluorescence

CFM-4 Chlorophyll Fluorescence Module

You can measure leaf gas exchange and chlorophyll fluorescence simultaneously with the CIRAS-4 Portable Photosynthesis System & CFM-4 Chlorophyll Fluorescence Module.

OJIP fast-induction kinetics

When performing measurements of photosynthesis and chlorophyll fluorescence that include an initial and/or concluding Fv/Fm measurement, the system will automatically generate a “fast fluorescence” file containing the fast-induction kinetics data needed for more detailed OJIP analysis based on the Fv/Fm measurements, and post-processing couldn’t be faster or easier!

Fast-fluorescence induction kinetics (OJIP) can provide valuable insight into the photochemical activity of Photosystem II & the electron transport chain.

MultiPulse™ Technology for Accurate Estimation of Fm

The CFM-4 is capable of delivering high-saturating pulses up to 10000 µmol m-2 s-1 which is extremely useful in accommodating a wider range of ambient light conditions. The CIRAS-4 is the only system available that features our innovative MultiPulse™ technology.

MultiPulse produces a sequence of user-defined, lower-saturating pulse light levels, avoiding the risk of photodamage to the leaf while accurately estimating apparent Fm‘.

A pulse-amplitude-modulated (PAM) fluorometer, the CFM-4 provides both dark- and light-adapted chlorophyll fluorescence measurement parameters including photochemical vs. non-photochemical quenching and electron transport rate.

Automatic control

The CFM-4 offers automatic control of temperature and light intensity (0-2500 µmol m-2 s-1) as well as ratio of red/green/blue/white LEDs, and far-red (0-30% of PAR).

A multi-use accessory!

The CFM-4 is elegantly designed with all light sources and fluorescence detection capability built directly into one lightweight, compact unit. The CFM-4 is a pulse-amplitude-modulated (PAM) fluorometer that can also act as an actinic light source for leaf gas exchange.

Advanced intuitive software

Advanced touch navigation & outstanding readability.

The CIRAS-4 offers highly responsive advanced touch navigation for all system operations from its large, full-color sunlight-readable touchscreen offering unsurpassed readability even under high sunlight conditions.

easy-to-use software

Your data your way

It’s all about the data. Not only can you trust the CIRAS-4 to provide highly accurate data quickly, you can customize your entire data collection and research experience all from the touchscreen.

Custom data files and comments

Create your own unique file names using letters, numbers, and symbols, and adding comments for further detail is quick and easy.

alphanumeric onscreen keyboard

Choose how you view your data

Graph up to six parameters at a time during measurement including zoom, pause, and resume, and easily customize the X and Y axis for each parameter.

Graph up to 6 parameters at once

Monitor measurements remotely

Monitoring measurements locally and remotely is easy with the CIRAS-4 Portable Photosynthesis System. Simply clamp your leaf into the cuvette, start your measurement and follow it in real-time on your PC or tablet!

Measurements in minutes

Got a question? Built-in system help and user tutorials are designed to guide even the most inexperienced user every step of the way. technology.

Unique multi-user profile system

Set up to eight unique profiles based on application, user, experiment, etc.—very useful when multiple users share a single system.

multi-user profile screen

Stability criteria

Set your own stability criteria for up to 12 parameters to alert you and the system when measurements are stable and ready to record.

Rapid A/Ci Curves in Minutes with the SSCO2R™ Method

SSCO2R Method™

The Single-Step CO2 Response Method – No empty chamber step or post processing needed!

The SSCO2R Method is a new high-speed ramping technique that eliminates all post-processing, allowing A-Ci curves to be produced in real time directly on the CIRAS-4 console.

Photosynthetic acclimation to temperature is affected by night temperature in Zea mays
J Bunce – Photosynthetica, 2024

Our Original High-Speed CO₂ Ramping Technique

The CIRAS-4 has the ability to rapidly change the CO₂ gas concentration while simultaneously and continuously recording data. Linear ramps of CO₂ concentration are even simpler to program and record than in previous instruments. Now that there is no longer a need to define a response script for a ramp test in the CIRAS-4, the process is faster than ever.