MAJOR – series

A Series of Digital Photodiode Sensors (DPDS)

» Posted on 10. Aug 2013

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MAJOR – A series of Photodiode Modules

 

LASER COMPONENTS is introducing a complete new series of digital photodiode sensors, which are based on the ACU2 modules: The MAJOR-series. These sensor modules are universal and highly flexible and can be integrated into existing or new systems. They might also find their usage as OEM products into other systems. The product family contains following main groups:

 
  • C-MAJOR: SiC, 220 nm to 380 nm
  • D-MAJOR: InGaAs, 500 nm to 1700 nm
  • E-MAJOR: Extended InGaAs, 650 nm to 2200/2600 nm

All MAJOR modules are assembled into a M12x1 screw housing and all versions are able to communicate via RS-232. From interfacing point of view these modules are grouped into two types:

 
  1. MAJOR-A modules with analog & digital outputs for single usages
  2. MAJOR modules with only digital interfaces for chaining and networking of modules

The electronic in both groups is the same. Due to limited number of output pins in a M12 housing, only 8 of 12 available signals can be routed to the output connector. This fact creates these two general groups of product families followed by a third possible customized variant for sending and receiving triggering impulses. While the first group is focused on single sensor applications – serving digital and analog sampling results to a host, the second group is focused on chained applications, where multiple sensors provide their sampling results digitally over one shared RS232 chained bus to a host.

When digital chaining is desired, there is no limit for the number of MAJOR modules in a chain and how long the chain gets as long as the distance between two sequential modules doesn’t exceed approx. 30 meters. This type of MAJOR module has two independent RS232 interfaces. Therefore they can be chained to each other and digital data can travel from one end to the other end of the chain. The limitation in this type of configuration is the bandwidth. The amount of simultaneous data generated by several MAJOR modules has to share the available bandwidth given in the chain, which is 115200 baud maximum.

MAJOR-A modules have only one digital and one analog interface pair. So they can’t be chained. But this type of modules provides a host the sampling result not only in digital form, but also as conditioned analog values. The temperature is also available to the host as an analog value. One of the analog outputs is the conditioned sensor value, which is presented at the same time also to the internal ADC and the other analog output can be a voltage in correlation to the sensor temperature or any other desired value controlled by the firmware (user application programmable).

 

Features

 
  • Small form factor (M12 housing 65mm long)
  • Complete integrated sensor signal conditioning and processing
  • Including a 12-bit up to 200ksps ADC with scaleable dynamic range
  • Sensor sensitivities up to 4µV/LSB with auto gain capability
  • Temperature and noise compensation algorithms
  • Capable of storing sampled sensor data together with temperature and time stamps
  • Providing digital and analog sensor data on its 8 pin interface
  • Digital communication over RS-232 lines: sensor-to-sensor & sensor-to-host (PC)
  • Two independent RS-232 channels for chaining of sensors
  • Host independent intercommunication of sensors and actors in a chain
  • Possibility to port and integrate user applications

 

Latest MAJOR modules

MAJOR modules with sensors based on InGaAsx-InGaAsPbsPbSe or SiC materials are built by detectors from Laser Components in Germany. Due to a product based cooperation, Laser Components has exclusive marketing and sales rights for this type of modules.

Following MAJOR modules are available at Laser Components known as Digital Photodiode Sensors:

  Article #   Name   DPDS modules with digital & analog outputs
  3009081   C-MAJOR-4-1212-1.0-A   SiC Digital Photodiode 1.6mm²
  3009082   C-MAJOR-4-2525-1.0-A   SiC Digital Photodiode 5mm²
  3009083   C-MAJOR-4E-0505-1.0-A   SiC Digital Photodiode 0.5×0.5mm², eryth.
  3009085   C-MAJOR-4-1010-1.0-A   SiC Digital Photodiode 0.965mm², TO18
  3009086   D-MAJOR-17-3000-1.0-A   InGaAs Digital Photodiode, 3mm, 1.7µm
  3009087   D-MAJOR-17-1000-1.0-A   InGaAs Digital Photodiode, 1mm, 1.7µm
  3009088   E-MAJOR-22-1000-1.0-A   x-InGaAs Digital Photodiode, 1mm, 2.2µm
  3009089   E-MAJOR-26-1300-1.0-A   x-InGaAs Digital Photodiode, 1.3mm, 2.6µm

 

Brief Introduction

The modules are capable of sensing, conditioning, processing and storing sensor data without additional or external processing power. Results may be compared to user defined thresholds for generating digital messages to the environment, storing them inside the sensor itself or shift them out directly to a host via its RS-232 interface.

 ACU2_block_diagram

As shown in the block diagram, the modules are generally built with an internal fixed temperature sensor and a programmable analog front end for interfacing various types of sensors. An integrated A/D converter and a 16-bit µController together with 4MB of Flash storage makes the modules ideal for many applications in the industry.

Digital processing of the module is based on a 16-bit RISC processor with 16 MIPS, 128kByte Flash and 10kByte SRAM. The ADC module is a µController built-in peripheral with a 200ksps fast 12-bit SAR analog-to-digital converter including a reference generator for sensor biasing.

The analog sensor signal gets conditioned by a programmable gain amplifier (PGA), which can be controlled by the firmware. It is then served to the ADC with the desired gain. At the same time an offset voltage can be applied to the system to blend out any unwanted signal levels or noises. The dynamic input range can be matched perfectly to the 2.5V dynamic range of the 12-bit A/D converter.

The electronic is capable of a total trans-impedance gain of 1,28·108V/A. This gain is built by a trans-impedance gain part expressed by 10mV/A with m = { 1 to 6 } and a voltage-gain part expressed by 2n with n = { 0 to 7}. The voltage gain is controlled by the PGA over the firmware, while the trans-impedance-gain is fixed by a resistor during manufacturing time. The trans-impedance gain gets defined by used sensor type and the desired sensitivity range.

The digital Interface is built by a RS232 transceiver with three driving and five receiving pins. All pins are protected to ±8kV using the IEC 61000-4-2 Air-Gap discharge method, ±8kV using the IEC61000-4-2 Contact Discharge method, and ±15kV using the Human-Body Model.

The analog outputs are capable of high-output-drive by CMOS op amps featuring 200mA of peak output current while they remain stable for capacitive loads up to 780pF. The output amplifier exhibits a high slew rate of 10V/µs and a gain-bandwidth product (GBWP) of 10MHz.

Sampled sensor data can be transferred to a PC as raw data – to databases or custom applications – or as user friendly verbose characters to be displayed on a PC using a hyper terminal. Any PDS module accepts user commands to generate various types of data outputs needed by the user.

 

InGaAs Photodiodes series IG17

The IG17-series is a panchromatic PIN photodiode with a nominal wavelength cut-off at 1.7 µm. This series has been designed for demanding spectroscopic and radiometric applications. It offers excellent shunt resistance in combination with superior responsivity over a wide range.

 

FEATURES

 
  • 50 % Cut-off Wavelength ≥ 1.65µm
  • Typical Peak Responsivity: 1.05 A/W
  • Excellent Temperature Stability
  • Reduced Edge Effect

 

APPLICATIONS

 
  • Spectrophotometer
  • Diode Laser Monitoring
  • Non-Contact Temperature Measurement
  • Flame Control
  • Moisture Monitoring

 

Electro-Optical Characteristics

 


Part Number

Diameter
[µm]
Shunt Impedance
@ VR= 10 mV
[MOhm]
Dark Current
@ VR= 5 V
[nA]
Capacitance
@ VR= 0 V
[pF]
Forward
Voltage
[V]
    Min. Typ. Typ. Max. Typ.  
IG17X250S4i 250 200 830 0.4 4 15 0.73
IG17X1000S4i 1000 20 75 2 20 215
IG17X1300S4i 1300 10 40 5 50 305
IG17X2000G1i 2000 5 25 10 100 700
IG17X3000G1i 3000 3 15 20 200 1550

 

 Ideal Diode ID Dark Current
IPH Photo Current
IR Noise Current
CS Shunt Capacitance
RP Parallel Impedance
or Shunt Impedance

 

MAJOR_Photosensitivity_Linearity

 

MAJOR_Spectral_Responce

 

MAJOR_Shunt_resistance_vs_Temperature

 

IG17series_current_Irradiance

 

MAJOR module Operation Mode

 

Photodiode_operation

 

There are two common operation modes for a photodiode detector. The sensor modules are configured in Photovoltaic mode, means UR=0 and therefore ID=0. The capacitance CS gets larger when no external biasing voltage is applied. Although this mode has slower response times in compare to the photodiode operation mode, it tends to exhibit less noise, resulting in more precise measurements.

Regardless of selected detector, the electronic in the module only observes the voltage over the load resistor RL. The blue line shows where the RL is configured in standard modules.

The incident radiation generates a photocurrent IPH loaded by diode characteristics and an external load resistor RL. When RL<<RP (at least factor 1000) then other parts of the equivalent circuit like parallel capacitance CS and shunt resistance RP are negligible leakages. They are ignored together with the noise current IR in standard modules with photovoltaic configuration. The ADC in the module measures the shunt resistor voltage expressed by RL·IS after conditioning it. The maximum shunt resistor voltage value has to remain below forward voltage of the photodiode, which is declared at 730mV for the IG17-series of photodiodes. The limit chosen for the IG17 series of detectors when observing RL·IS is defined at 500mV.

 

Module Characteristics

 

MAJOR_conversion_characteristics

 

Standard sensor modules are optimized for measuring weak signal intensities. Considering the 500mV as the maximum dynamic range for the detector output and a built-in shunt resistor of RL=10kΩ in the standard sensor modules, results in a dynamic light intensity range, which shouldn’t exceed photo currents over IPH=50µA. Both the “Photosensitivity Linearity” and “Current Power Density” curves above show in these lower areas absolute linear relationships.

All the negligible currents explained before including the noise current IR together with unwanted ambient incident light generate an unwanted total current through RL, generating an unwanted noise voltage in front of the sensors’ ADC input. This voltage can be compensated with a software controlled offset voltage Voffset to hide it completely from being measured and wasting the dynamic range of the ADC input.

Depending on application needs, the user can now zoom into an area of detector output voltage for measuring sensor values by applying related gain and offset voltages as shown in figure above.

 

MAJOR Related Information and Links

 

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