Apogee Instruments SE-100 Photometric Sensor

Certificate of Compliance

EU Declaration of Conformity

This declaration of conformity is issued under the sole responsibility of the manufacturer: Apogee Instruments, Inc. 721 W 1800 N Logan, Utah 84321 USA

Product(s): Models: SE-100, Type: Photometric Sensors

The object of the declaration described above is in conformity with the relevant Union harmonization legislation:

• 2014/30/EU Electromagnetic Compatibility (EMC) Directive
• 2011/65/EU Restriction of Hazardous Substances (RoHS 2) Directive
• 2015/863/EU Amending Annex II to Directive 2011/65/EU (RoHS 3)

Standards referenced during compliance assessment:

• EN 61326-1:2013 Electrical equipment for measurement, control and laboratory use – EMC requirements
• EN 50581:2012 Technical documentation for the assessment of electrical and electronic products with respect to the restriction of hazardous substances

Apogee Instruments, Inc. states that their products do not contain, as intentional additives, any of the restricted materials including lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), polybrominated diphenyls (PBDE), bis(2-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), and diisobutyl phthalate (DIBP). Articles containing greater than 0.1% lead concentration are RoHS 3 compliant using exemption 6c. Apogee Instruments does not run analysis on raw materials or end products for these substances but relies on supplier information.

Signed for and on behalf of: Apogee Instruments, June 2020

Bruce Bugbee
President
Apogee Instruments, Inc.

Introduction

The human eye is sensitive to radiation from about 380 to 780 nm, with peak sensitivity near 555 nm. The photopic luminosity function (CIE 1931 standard) describes average human sensitivity to brightness in well-lit conditions. The scotopic luminosity function describes sensitivity in dimly-lit conditions.

Illuminance is the measurement of radiant energy on a surface, weighted by human eye response. It is quantified in lux or footcandles. Lux is lumens per square meter (lm m⁻²), and footcandles is lumens per square foot (lm ft⁻²). 1 square meter equals 10.7639 square feet. Sensors measuring illuminance are also called light sensors, photometric radiometers, photopic sensors, and lux sensors.

Typical applications include determining optimum light levels in indoor environments and quantifying material/substance exposure to light.

Apogee Instruments SE series photometric sensors consist of a cast acrylic diffuser, optical filter, photodiode, signal processing circuitry in an anodized aluminum housing, and a cable. They are designed for continuous illuminance measurement in indoor and outdoor environments. SE-100 and SE-200 series sensors output an analog voltage proportional to illuminance incident on a planar surface from all angles of a hemisphere.

Sensor Models

This manual covers the unamplified model SE-100. Additional models are covered in their respective manuals.

Sensor model number and serial number are located on the bottom of the sensor. Contact Apogee Instruments with the serial number for manufacturing date information.

Specifications

Calibration Traceability

Apogee SE series photometric sensors are calibrated by comparing them to the mean of four transfer standard SE-100 photometric sensors under a reference lamp. The transfer standards are calibrated against at least two reference photometric sensors. The reference sensors are recalibrated biannually using a quartz halogen lamp traceable to the National Institute of Standards and Technology (NIST).

Spectral Response

The graph shows the mean relative spectral response of four SE-100 photometric radiometers (green line) compared to the CIE-1931 curve (dotted line). The response peaks around 555 nm.

Cosine Response

Directional, or cosine, response is defined as the measurement error at a specific angle of radiation incidence. Error for Apogee SE series photometric sensors is approximately ± 2% and ± 5 % at solar zenith angles of 45° and 75°, respectively. The graph illustrates the cosine response measurements, showing the error percentage relative to the solar zenith angle.

Deployment and Installation

Mount the sensor to a solid surface using the provided nylon mounting screw to prevent galvanic corrosion. Ensure the sensor is level for accurate horizontal illuminance measurement. An Apogee Instruments model AL-100 Leveling Plate is recommended for flat surfaces or wood mounting. For mast or pipe mounting, the Apogee Instruments model AL-120 Solar Mounting Bracket with Leveling Plate is recommended.

To minimize azimuth error, point the cable toward true north (northern hemisphere) or true south (southern hemisphere). Azimuth error is typically less than 1% and can be minimized by proper cable orientation.

Orient the cable towards the nearest pole and mount the sensor to avoid obstructions that could shade it (e.g., weather station tripod/tower). After mounting, remove the green cap; it can be used as a protective cover when the sensor is not in use.

Cable Connectors

Apogee sensors feature ruggedized M8 connectors (IP68 rated, marine-grade stainless-steel) for simplified sensor removal for calibration. Inline cable connectors are installed 30 cm from the sensor head.

Instructions:

• Pins and Wiring Colors: Connectors have six pins, but not all are used for every sensor. Unused wire colors may be present inside the cable.
• Replacement Cable: Contact Apogee directly for replacement cables to ensure correct pigtail configuration.
• Alignment: Arrows on the connector jacket and an aligning notch ensure proper orientation during reconnection.
• Disconnection: For extended periods, protect the station-side connector from water and dirt with electrical tape.
• Tightening: Finger-tighten connectors only. Overtightening can compress the o-ring. Ensure proper thread alignment to avoid cross-threading. 1-2 threads may still be visible when fully tightened.

WARNING: Do not twist the black cable or sensor head when tightening; twist only the metal connector.

When sending sensors for calibration, send only the short end of the cable and half the connector.

Operation and Measurement

Connect the sensor to a measurement device (meter, datalogger, controller) capable of measuring and displaying or recording a millivolt signal (0-150 mV range recommended). Match the measurement device's input range to the sensor's output range for optimal resolution and signal-to-noise ratio.

DO NOT connect the sensor to a power source. The sensor is self-powered; applying voltage will damage it.

Wiring for SE-100:

• White wire: Output Signal
• Black wire: Ground
• Clear wire: Shield

Sensor Calibration

The Apogee unamplified photometric sensor model SE-100 has a standard illuminance (lux) calibration factor of 1000 lux per mV.

To convert sensor output (mV) to illuminance (lux), multiply the measured mV signal by the calibration factor:

Calibration Factor (1000 lux per mV) * Sensor Output Signal (mV) = lux (lm m⁻²)

Example: Full sunlight (approx. 120000 lux) yields a sensor output of 120 mV. Multiplying 120 mV by the calibration factor of 1000 lux/mV gives 120000 lux.

Spectral Errors

Spectral errors occur when the radiometer's spectral response does not perfectly match the CIE 1931 photopic luminosity function, especially with light sources that differ from the calibration source. The table below provides spectral error estimates for Apogee SE-100 series photometric radiometers under various light sources, calculated relative to Sun (Clear Sky).

Maintenance and Recalibration

Blocking of the optical path by moisture, debris, dust, or salt deposits can cause low readings. Clean the diffuser and apertures as needed.

1. Moisture or debris on the diffuser or in the apertures.
2. Dust during periods of low rainfall.
3. Salt deposit accumulation from sea spray or sprinkler irrigation water.

For dust or organic deposits, use water or window cleaner with a soft cloth or cotton swab. Dissolve salt deposits with vinegar and remove with a cloth or cotton swab. Salt deposits cannot be removed with solvents like alcohol or acetone. Use gentle pressure to avoid scratching the diffuser. Use only mechanical force for cleaning, not abrasive materials or cleaners.

It is recommended that two-band sensors be recalibrated every two years. For details on returning sensors for recalibration, visit the Apogee webpage: http://www.apogeeinstruments.com/tech-support-recalibration-repairs/.

Troubleshooting and Customer Support

Independent Verification of Functionality

Check sensor functionality using a voltmeter with millivolt resolution. Connect the voltmeter's positive lead to the sensor's white wire and the negative lead to the black wire. Direct the sensor toward a light source; a signal should be produced. Varying the distance to the light source should proportionally change the signal. Blocking all radiation should result in a zero signal.

Compatible Measurement Devices (Dataloggers/Controllers/Meters)

The SE-100 sensor has a calibration factor of 1000 lux per mV, yielding a sensitivity of 0.001 mV per lux. A compatible measurement device should have a resolution of at least 0.001 mV for 1 lux illuminance resolution.

An example datalogger program for Campbell Scientific dataloggers is available at: https://www.apogeeinstruments.com/content/Photometric-Unamplified.CR1.

Cable Length

Sensor output signals are not affected by shortening or splicing cables, provided the measurement device has high input impedance (greater than 1 mega-ohm). Apogee sensors use shielded, twisted pair cable to minimize electromagnetic interference. For best measurements, connect the shield wire to an earth ground, especially in noisy environments or with long lead lengths.

Modifying Cable Length

For details on extending sensor cable length, see the Apogee webpage: http://www.apogeeinstruments.com/how-to-make-a-weatherproof-cable-splice/.