	SQ-100X	SQ-202X	SQ-204X	SQ-205X	SQ-301X	SQ-420X	SQ-421X	SQ-422X
Power Supply	Self-powered	5 to 24 V DC	7 to 24 V DC	5.5 to 24 V DC	Self-powered	5 V USB power source	5.5 to 24 V DC	5.5 to 24 V DC
Current Draw	-	10 µA	22 mA maximum; 2 mA quiescent	10 µA	-	61 mA when logging	1.4 mA (quiescent); 1.8 mA (active)	RS-232 quiescent 36.87 mA, active 37.06 mA; RS-485 quiescent 37.37 mA, active 42.30 mA
Output (Sensitivity)	0.1 mV per µmol m^-2 s^-1	0.6 mV per µmol m^-2 s^-1	0.004 mA per µmol m^-2 s^-1	1.25 mV per µmol m^-2 s^-1	0.1 mV per µmol m^-2 s^-1	-	-	-
Output Type	0 to 250 mV	0 to 2.5 V	4 to 20 mA	0 to 5 V	0 to 250 mV	USB	SDI-12	Modbus
Resolution	-	-	-	-	-	0.1 µmol m^-2 s^-2	-	-
Calibration Factor (reciprocal of sensitivity)	10 µmol m^-2 s^-1 per mV	1.6 µmol m^-2 s^-1 per mV	250 µmol m^-2 s^-1 per mV	0.8 µmol m^-2 s^-1 per mV	10 µmol m^-2 s^-1 per mV	Custom for each sensor and stored in the firmware	Custom for each sensor and stored in the firmware	Custom for each sensor and stored in the firmware
Calibration Uncertainty	± 5 %	± 5 %	± 5 %	± 5 %	± 5 %	± 5 %	± 5 %	± 5 %
Measurement Repeatability	Less than 0.5 %	Less than 0.5 %	Less than 0.5 %	Less than 0.5 %	Less than 0.5 %	Less than 0.5 %	Less than 1 %	Less than 1 %
Long-term Drift	Less than 2 % per year	Less than 2 % per year	Less than 2 % per year	Less than 2 % per year	Less than 2 % per year	Less than 2 % per year	Less than 2 % per year	Less than 2 % per year
Non-linearity	Less than 1 % (up to 2500 µmol m^-2 s^-1)	Less than 1 % (up to 4000 µmol m^-2 s^-1)	Less than 1 % (up to 4000 µmol m^-2 s^-1)	Less than 1 % (up to 4000 µmol m^-2 s^-1)	Less than 1 % (up to 2500 µmol m^-2 s^-1)	Less than 1 % (up to 2500 µmol m^-2 s^-1)	Less than 1 % (up to 2500 µmol m^-2 s^-1)	Less than 1 % (up to 2500 µmol m^-2 s^-1)
Response Time	Less than 1 ms	Less than 1 ms	Less than 1 ms	Less than 1 ms	Less than 1 ms	Software updates every second	Less than 0.6 s	-
Field of View	180°	180°	180°	180°	180°	180°	180°	180°
Spectral Range	370 to 650 nm (wavelengths where response is greater than 50 % of maximum)	370 to 650 nm (wavelengths where response is greater than 50 % of maximum)	370 to 650 nm (wavelengths where response is greater than 50 % of maximum)	370 to 650 nm (wavelengths where response is greater than 50 % of maximum)	370 to 650 nm (wavelengths where response is greater than 50 % of maximum)	370 to 650 nm (wavelengths where response is greater than 50 % of maximum)	370 to 650 nm (wavelengths where response is greater than 50 % of maximum)	370 to 650 nm (wavelengths where response is greater than 50 % of maximum)
Directional (Cosine) Response	± 5 % at 75° zenith angle	± 5 % at 75° zenith angle	± 5 % at 75° zenith angle	± 5 % at 75° zenith angle	± 5 % at 75° zenith angle	± 5 % at 75° zenith angle	± 5 % at 75° zenith angle	± 5 % at 75° zenith angle
Temperature Response	-0.04 % per C	0.06 ± 0.06 % per C	0.06 ± 0.06 % per C	0.06 ± 0.06 % per C	-0.04 % per C	-0.04 % per C	0.06 ± 0.06 % per C	0.06 ± 0.06 % per C
Operating Environment	-10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m	-10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m	-10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m	-10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m	-10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m	-10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m	-10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m	-10 to 60 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m
Dimensions	24 mm diameter, 33 mm height	30.5 mm diameter, 37 mm height	30.5 mm diameter, 37 mm height	30.5 mm diameter, 37 mm height	616.4 mm length, 13.6 mm height, 16.5 mm width	24 mm diameter, 33 mm height	30.5 mm diameter, 37 mm height	30.5 mm diameter, 37 mm height
Mass (with 5 m of cable)	90 g	140 g	140 g	140 g	310g	90 g	140 g	140 g