apogee SI-4H1 Infrared Radiometers Owner’s Manual

OWNER’S MANUAL
INFRARED RADIOMETER
Models SI-411, SI-421, SI-431, and SI-4H1
(including SS models)

APOGEE INSTRUMENTS, INC.
721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA TEL: 435-792-4700 | FAX: 435-787-8268
WEB: APOGEEINSTRUMENTS.COM

DECLARATION OF CONFORMITY

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

for the following product(s):

Models: SI-411, SI-421, SI-431, SI-4H1 Type: Infrared Radiometer

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

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

Please be advised that based on the information available to us from our raw material suppliers, the products manufactured by us do not contain, as intentional additives, any of the restricted materials including cadmium, hexavalent chromium, lead, mercury, polybrominated biphenyls (PBB), polybrominated diphenyls (PBDE).
Further note that Apogee Instruments does not specifically run any analysis on our raw materials or end products for the presence of these substances, but rely on the information provided to us by our material suppliers.

Signed for and on behalf of:
Apogee Instruments, May 2016

Bruce Bugbee
President
Apogee Instruments, Inc.

INTRODUCTION

All objects with a temperature above absolute zero emit electromagnetic radiation. The wavelengths and intensity of radiation emitted are related to the temperature of the object. Terrestrial surfaces (e.g., soil, plant canopies, water, snow) emit radiation in the mid infrared portion of the electromagnetic spectrum (approximately 4-50 µm).
Infrared radiometers are sensors that measure infrared radiation, which is used to determine surface temperature without touching the surface (when using sensors that must be in contact with the surface, it can be difficult to maintain thermal equilibrium without altering surface temperature). Infrared radiometers are often called infrared thermometers because temperature is the desired quantity, even though the sensors detect radiation.
Typical applications of infrared radiometers include plant canopy temperature measurement for use in plant water status estimation, road surface temperature measurement for determination of icing conditions, and terrestrial surface (soil, vegetation, water, snow) temperature measurement in energy balance studies.
Apogee Instruments SI series infrared radiometers consist of a thermopile detector, germanium filter, precision thermistor (for detector reference temperature measurement), and signal processing circuitry mounted in an anodized aluminum housing, and a cable to connect the sensor to a measurement device. All radiometers also come with a radiation shield designed to minimize absorbed solar radiation, but still allowing natural ventilation. The radiation shield insulates the radiometer from rapid temperature changes and keeps the temperature of the radiometer closer to the target temperature. Sensors are potted solid with no internal air space and are designed for continuous temperature measurement of terrestrial surfaces in indoor and outdoor environments. SI-400 series sensors output a digital signal using SDI-12 protocol version 1.3.

SENSOR MODELS

Sensor model number and serial number are located on a label near the pigtail leads on the sensor cable. If you need the manufacturing date of your sensor, please contact Apogee Instruments with the serial number of your sensor.

The four FOV options and associated model numbers are shown below:

SPECIFICATIONS

| SI-411| SI-421| SI-431| SI-4H1
---|---|---|---|---
Input Voltage Requirement| 5.5 to 24 V DC
Current Drain| 0.6 mA (quiescent),1.3 mA (active)
Calibration Uncertainty (-20 to 65 C),
when target and detector temperature are
within 20 C| 0.2 C| 0.2 C| 0.3 C| 0.2 C
Calibration Uncertainty (-40 to 80 C),
when target and detector temperate are
different by more than 20 C
(see Calibration Traceability below)| 0.5 C| 0.5 C| 0.6 C| 0.5 C
Measurement Repeatability| less than 0.05 C
Stability (Long-term Drift)| less than 2 % change in slope per year when germanium filter is maintained in a
clean condition (see Maintenance and Recalibration section below)
Response Time| 0.6 s, time for detector signal to reach 95 % following a step change; fastest data
transmission rate for SDI-12 circuitry is 1 s
Response Time| 22º half angle| 18º half angle| 14º half angle| 32º horizontal half
angle; 13º vertical
half angle
Spectral Range| 8 to 14 µm; atmospheric window (see Spectral Response below)
Operating Environment| -45 to 80 C; 0 to 100 % relative humidity (non- condensing)
Dimensions| 23 mm diameter; 60 mm length
Mass| 190 g (with 5m of lead wire)
Cable| 5 m of two conductor, shielded, twisted-pair wire; additional cable available in
multiples of 5 m; santoprene rubber jacket (high water resistance, high UV stability,
flexibility in cold conditions); pigtail lead wires

Calibration Traceability
Apogee SI series infrared radiometers are calibrated to the temperature of a custom blackbody cone held at multiple fixed temperatures over a range of radiometer (detector/sensor body) temperatures. The temperature of the blackbody cone is measured with replicate precision thermistors thermally bonded to the cone surface. The precision thermistors are calibrated for absolute temperature measurement against a platinum resistance thermometer (PRT) in a constant temperature bath. The PRT calibration is directly traceable to the NIST.

Spectral Response

Spectral response of SI series infrared radiometers. Spectral response (green line) is determined by the germanium filter and corresponds closely to the atmospheric window of 8-14 µm, minimizing interference from atmospheric absorption/emission bands (blue line) below 8 µm and above 14 µm. Typical terrestrial surfaces have temperatures that yield maximum radiation emission within the atmospheric window, as shown by the  lackbody
curve for a radiator at 28 C (red line).

DEPLOYMENT AND INSTALLATION

The mounting geometry (distance from target surface, angle of orientation relative to target surface) is determined by the desired area of surface to be measured. The field of view extends unbroken from the sensor to the target surface. Sensors must be carefully mounted in order to view the desired target and avoid including unwanted surfaces/objects in the field of view, thereby averaging unwanted temperatures with the target temperature (see Field of View below). Once mounted, the green cap must be removed. The green cap can be used as a protective covering for the sensor, when it is not in use.
An Apogee Instruments model AM-210 mounting bracket is recommended for mounting the sensor to a cross arm or pole. The AM-210 allows adjustment of the angle of the sensor with respect to the target and accommodates the radiation shield designed for all SI series infrared radiometers.

Field of View
The field of view (FOV) is reported as the half-angle of the apex of the cone formed by the target surface (cone base) and the detector (cone apex), as shown below, where the target is defined as a circle from which 98 % of the radiation detected by the radiometer is emitted.

Sensor FOV, distance to target, and sensor mounting angle in relation to the target will determine target area.
Different mounting geometries (distance and angle combinations) produce different target shapes and areas, as shown below.

A simple FOV calculator for determining target dimensions based on infrared radiometer model, mounting height, and mounting angle, is available on the Apogee website: http://www.apogeeinstruments.com/using-your- apogeeinstruments-infrared-radiometer/.

CABLE CONNECTORS

Apogee started offering in-line cable connectors on some bare-lead sensors in March 2018 to simplify the process of removing sensors from weather stations for calibration by not requiring the full cable to be uninstalled back to the data logger.
The ruggedized M8 connectors are rated IP67, made of corrosion-resistant marine-grade stainless-steel, and designed for extended use in harsh environmental conditions.

Instructions
Pins and Wiring Colors: All Apogee connectors have six pins, but not all pins are used for every sensor. There may also be unused wire colors inside the cable. To simplify data logger connection, we remove the unused pigtail lead colors at the data logger end of the cable.
If you ever need a replacement cable, please contact us directly to ensure ordering the proper pigtail configuration.
Alignment: When reconnecting your sensor, arrows on the connector jacket and an aligning notch ensure proper orientation.
Disconnection for extended periods: When disconnecting the sensor for an extended period of time from a station, protect the remaining half of the connector still on the station from water and dirt with electrical tape or other method.
Tightening: Connectors are designed to be firmly finger-tightened only. There is an o-ring inside the connector that can be overly compressed if a wrench is used. Pay attention to thread alignment to avoid crossthreading. When fully tightened, 1-2 threads may still be visible.

Inline cable connectors are installed 30 cm from the head (pyranometer pictured)

A reference notch inside the connector ensures proper alignment before tightening.

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

Finger-tighten firmly

OPERATION AND MEASUREMENT

All SI-400 series radiometers have an SDI-12 output, where target and detector temperatures are returned in digital format. Measurement of SI-400 series radiometers requires a measurement device with SDI-12 functionality that includes the M or C command.
VERY IMPORTANT: Apogee changed all wiring colors of our bare-lead sensors in March 2018 in conjunction with the release of inline cable connectors on some sensors. To ensure proper connection to your data device, please note your serial number or if your sensor has a stainless-steel connector 30 cm from the sensor head then use the appropriate wiring configuration below.

Wiring for SI-400 Series with Serial Numbers range 0-3056

Wiring for SI-400 Series with Serial Numbers 3057 and above or with a cable connector

Sensor Calibration
Apogee SI series infrared radiometers are calibrated in a temperature controlled chamber that houses a custombuilt blackbody cone (target) for the radiation source. During calibration, infrared radiometers (detectors) are held in a fixture at the opening of the blackbody cone, but are thermally insulated from the cone. Detector and target temperature are controlled independently. At each calibration set point, detectors are held at a constant temperature while the blackbody cone is controlled at temperatures below (12 C), above (18 C), and equal to the detector temperature. The range of detector temperatures is -15 C to 45 C (set points at 10 C increments). Data are collected at each detector temperature set point, after detectors and target reach constant temperatures.
All Apogee SDI-12 infrared radiometer models (SI-400 series) have sensor- specific calibration coefficients determined during the custom calibration process. Coefficients are programmed into the microcontroller at the factory. Calibration data for each sensor are provided on a calibration certificate (example shown on following page).

Calibration overview data are listed in box in upper left-hand corner, temperature errors are shown in graph, and calibration date is listed below descriptions of calibration procedure and traceability.

SDI-12 Interface
The following is a brief explanation of the serial digital interface SDI-12 protocol instructions used in Apogee SI-400 series infrared radiometers. For questions on the implementation of this protocol, please refer to the official version of the SDI-12 protocol: http://www.sdi-2.org/specification.php (version 1.4, August 10, 2016).

Overview
During normal communication, the data recorder sends a packet of data to the sensor that consists of an address and a command. Then, the sensor sends a response. In the following descriptions, SDI-12 commands and responses are enclosed in quotes. The SDI-12 address and the command/response terminators are defined as follows:
Sensors come from the factory with the address of “0” for use in single sensor systems. Addresses “1 to 9” and “A to Z”, or “a to z”, can be used for additional sensors connected to the same SDI-12 bus.
“!” is the last character of a command instruction. In order to be compliant with SDI-12 protocol, all commands must be terminated with a “!”. SDI-12 language supports a variety of commands. Supported commands for the Apogee Instruments SI-400 series infrared radiometers are listed in the following table (“a” is the sensor address. The following ASCII Characters are valid addresses: “0-9” or “A-Z”).

Supported Commands for Apogee Instruments SI-400 Series Infrared Radiometers

Measurement and return it with a Check Character
Change Address Command| aAb!| Changes the Address of the Sensor from a to b
Concurrent Measurement Command| aC!| Used to take a measurement when more than one sensor is used on the same data line
Concurrent Measurement Command w/ Check Character| aCC!| Used to take a measurement when more than one sensor is used on the same data line. Data is returned with a check character.
Address Query Command| ?!| Used when the address is unknown to have the sensor identify its address
Get Data Command| aDO!| Retrieves the data from a sensor

Make Measurement Command: M!
The make measurement command signals a measurement sequence to be performed. Data values generated in response to this command are stored in the sensor’s buffer for subsequent collection using “D” commands. Data will be retained in sensor storage until another “M”, “C”, or “V” command is executed. M commands are shown in the following examples:

where a is the sensor address (“0-9”, “A-Z”, “a-z”) and M is an upper-case ASCII character.
The target temperature and sensor body temperature are separated by the sign “+” or “-“, as in the following example (0 is the address):

where 23.4563 is target temperature, 1.0 is target millivolts, and 35.1236 is detector (sensor body) temperature.

Concurrent Measurement Command: aC!
A concurrent measurement is one which occurs while other SDI-12 sensors on the bus are also making measurements. This command is similar to the “aM!” command, however, the nn field has an extra digit and the sensor does not issue a service request when it has completed the measurement. Communicating with other sensors will NOT abort a concurrent measurement. Data values generated in response to this command are stored in the sensor’s buffer for subsequent collection using “D” commands. The data will be retained in the sensor until another “M”, “C”, or “V” command is executed:

where a is the sensor address (“0-9”, “A-Z”, “a-z”, “*”, “?”) and C is an upper-case ASCII character.
For example (0 is the address):

where 23.4563 is target temperature, 1.0 is target millivolts, and 35.1236 is detector (sensor body) temperature.

Change Sensor Address: aAb!
The change sensor address command allows the sensor address to be changed. If multiple SDI-12 devices are on the same bus, each device will require a unique SDI-12 address. For example, two SDI-12 sensors with the factory address of 0 requires changing the address on one of the sensors to a non-zero value in order for both sensors to communicate properly on the same channel:

where a is the current (old) sensor address (“0-9”, “A-Z”), A is an upper-case ASCII character denoting the instruction for changing the address, b is the new sensor address to be programmed (“0-9”, “A-Z”), and ! is the standard character to execute the command. If the address change is successful, the datalogger will respond with the new address and a .

Send Identification Command: aI!
The send identification command responds with sensor vendor, model, and version data. Any measurement data in the sensor’s buffer is not disturbed:

identifying values are returned

where a is the sensor address (“0-9”, “A-Z”, “a-z”, “*”, “?”), mm is a the sensor model number (11, 21, 31, or H1), vvv is a three character field specifying the sensor version number, and xx…xx is serial number.

Metadata Commands
Identify Measurement Commands
The Identify Measurement Commands can be used to view the command response without making a measurement. The command response indicates the time it takes to make the measurement and the number of data values that it returns. It works with the Verification Command (aV!), Measurement Commands (aM!, aM1! … aM9!, aMC!, aMC1! … aMC9!), and Concurrent Measurement Commands (aC!, aC1! … aC9! , aCC!, aCC1! … aCC9!). The format of the Identify Measurement Command is the address, the capital letter I, the measurement command, and the command terminator (“!”), as follows: