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Transcript of Data Aquisition
Harvard Business Review
How to lower the cost of enterprise sales?
Sensors that convert physical parameters to electrical signals.
The Cost to Acquire a Customer (CAC) exceeds the Life Time Value (LTV) a customer brings us.
This is my third go-around selling to large enterprises, SkyStream, Kontiki and now Qumu.
I like to explain to you the problem the way I see it, the changes I suggest to avoid making the same mistake again. and
Travels to Clients
SlideRocket a-synchronous selling tool
LinkedIn as a Sales Tool
EchoSign - eSignatures for contracts
Step 4: Implement a weekly training program
Step 1: Elements of a SaaS Sales Machine
Training: Coach your team!
Organize like a sports team
Due to high amount of changes in our field we can no longer rely on training institutions, this is the coach responsibility
One Hour per week
(vs. annual 3-day training)
The Effective Minority
WHAT EXPERTS DO BEST
These are the skills that we must teach
Selling SaaS in the Enterprise
Hire and develop along Web-Selling Skills
Consultative with Provocative approach
Latest in asynchronous selling tools
Weekly training sessions with coach
Flat/Sport team like organization, compensated on Logo, Use and Seats
Most corporations get stuck at 100-300 customers
Customer Success Driven
RainKing - Get to the right prospects
Qvidian - Sales Playbooks
Box - Hosting key documents
In Texas Instrument
Data acquisition is the process of sampling signals that measure real world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems (abbreviated with the acronym DAS or DAQ) typically convert analog waveforms into digital values for processing.
The components of data acquisition
Signal conditioning circuitry to convert sensor signals into a form that can be converted to digital values
Analog-to-digital converters, which convert conditioned sensor signals to digital values
The measurement of a physical phenomenon, such as the temperature of a room, the intensity of a light source, or the force applied to an object, begins with a sensor. A sensor, also called a transducer, converts a physical phenomenon into a measurable electrical signal. Depending on the type of sensor, its electrical output can be a voltage, current, resistance, or another electrical attribute that varies over time. Some sensors may require additional components and circuitry to properly produce a signal that can accurately and safely be read by a DAQ device.
• DAQ Boards and Devices
DAQ hardware acts as the interface between a computer and signals from the outside world. It primarily functions as a device that digitizes incoming analog signals so that a computer can interpret them. The three key components of a DAQ device used for measuring a signal are the signal conditioning circuitry, analog-to-digital converter (ADC), and computer bus. Many DAQ devices include other functions for automating measurement systems and processes. For example, digital-to-analog converters (DACs) output analog signals, digital I/O lines input and output digital signals, and counter/timers count and generate digital pulses.
Key Measurement Components of a DAQ Device
Analog-to-Digital Converter (ADC)
DAQ hardware acts as the interface between a computer and signals from the outside world. It primarily functions as a device that digitizes incoming analog signals so that a computer can interpret them. The three key components of a DAQ device used for measuring a signal are the signal conditioning circuitry, analog-to-digital converter (ADC), and computer bus. Many DAQ devices include other functions for automating measurement systems and processes. For example, digital-to-analog converters (DACs) output analog signals, digital I/O lines input and output digital signals, and counter/timers count and generate digital pulses
Analog signals from sensors must be converted into digital before they are manipulated by digital equipment such as a computer. An ADC is a chip that provides a digital representation of an analog signal at an instant in time. In practice, analog signals continuously vary over time and an ADC takes periodic “samples” of the signal at a predefined rate. These samples are transferred to a computer over a computer bus where the original signal is reconstructed from the samples in software.
DAQ devices connect to a computer through a slot or port. The computer bus serves as the communication interface between the DAQ device and computer for passing instructions and measured data. DAQ devices are offered on the most common computer buses including USB, PCI, PCI Express, and Ethernet. More recently, DAQ devices have become available for 802.11 Wi-Fi for wireless communication. There are many types of buses, and each offers different advantages for different types of applications.
A thermocouple is a length of two wires made from two dissimilar conductors (usually alloys) that are soldered or welded together at one end as shown below. Seebeck, a German scientist, discovered that when two wires of dissimilar metals are connected together at both ends, and one end is heated with respect to the other; there is a continuous current that flows. This phenomenon is known as the Seebeck Effect. The magnitude and direction of the current is affected by the types of metals used, and the temperature difference between the hot and cold ends. Depending on the change in temperature that the thermocouple is subject to, a proportional voltage output is produced. It is a common misconception to believe that the voltage output is developed actually at the junction. In reality, this a voltage gradient along the 2 metal lines that we are measuring
Types of Thermocouples
Depending on the required temperature range, vibration resistance, chemical resistance, response time and equipment requirements the user may choose the appropriate thermocouple. Thermocouples are available on different combinations of metals and/or calibrations. The most common type of thermocouples are J, K, T, and E. Thermocouples R, S, C and GB are high temperature range thermocouples. The thermocouple maximum temperature also ranges with the diameter of the wire used.
Performing an accurate cold junction temperature measurement is essential for the accuracy of the thermocouple measurement. A thermistor, RTD or temperature sensing IC may be used to measure the temperature of the thermocouple connector and perform cold junction compensation. Both terminals of the thermocouple and the temperature sensing device must be at the same temperature or errors in the measurement may be introduced. In applications requiring high precision, the cold junction temperature sensor and the thermocouple terminals are placed on an isothermal block to keep them at the same temperature.
Cold Junction measurement
Low pass filter considerations:
It is generally recommended to place a first-order, low-pass, anti aliasing RC filter at the inputs of the ADC. However, avoid increasing the filter resistance beyond 1kOhm. When an excessively large filter resistance is used, this resistance will begin to interact with the ADC's input impedance, resulting in linearity and gain errors.
A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.
Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range, typically −90 °C to 130 °C.
Types of Thermistors
Positive-temperature coefficient, or PTC, thermistors increase their resistance as the temperature rises. The relationship between resistance and temperature is linear, as expressed in the following equation: deltaR = k(deltaT) where deltaR is the change in resistence, deltaT is the change in temperature and k is the temperature coefficient. When k is positive, it causes a linear increase in resistance as the temperature rises.
Negative-temperature coefficient, or NTC, thermistors decrease their resistance as the temperature rises. The same equation is used as in the PTC thermistor; however, the negative k creates a non-linear decrease in resistance as the temperature rises. Because of this, multiple NTC thermistors are often used in the same unit to normalize the drop in resistance.
PTC thermistors can be used as current-limiting devices for circuit protection, as replacements for fuses. Current through the device causes a small amount of resistive heating. If the current is large enough to generate more heat than the device can lose to its surroundings, the device heats up, causing its resistance to increase, and therefore causing even more heating. This creates a self-reinforcing effect that drives the resistance upwards, reducing the current and voltage available to the device.
PTC thermistors were used as timers in the degaussing coil circuit of most CRT displays. When the display unit is initially switched on, current flows through the thermistor and degaussing coil. The coil and thermistor are intentionally sized so that the current flow will heat the thermistor to the point that the degaussing coil shuts off in under a second. For effective degaussing, it is necessary that the magnitude of the alternating magnetic field produced by the degaussing coil decreases smoothly and continuously, rather than sharply switching off or decreasing in steps; the PTC thermistor accomplishes this naturally as it heats up. A degaussing circuit using a PTC thermistor is simple, reliable (for its simplicity), and inexpensive.
NTC thermistors are used as resistance thermometers in low-temperature measurements of the order of 10 K.
NTC thermistors can be used as inrush-current limiting devices in power supply circuits. They present a higher resistance initially which prevents large currents from flowing at turn-on, and then heat up and become much lower resistance to allow higher current flow during normal operation. These thermistors are usually much larger than measuring type thermistors, and are purposely designed for this application.
NTC thermistors are regularly used in automotive applications. For example, they monitor things like coolant temperature and/or oil temperature inside the engine and provide data to the ECU and, indirectly, to the dashboard.
NTC thermistors can be also used to monitor the temperature of an incubator.
Thermistors are also commonly used in modern digital thermostats and to monitor the temperature of battery packs while charging.
Thermistors are also used in the hot ends of 3d printers, they produce heat and keep a constant temperature for melting the plastic filament.
RTD stands for Resistance Temperature Detector. As the name suggests, RTDs produce a change in resistance in response to a change in temperature. RTDs are typically fabricated from Nickel (Ni), Copper (Cu), or Platinum (Pt) metals in the form of a wire or thin film. Construction from these metals allows for RTDs to be created in convenient sizes and standard resistances, where 100-Ohm and 1000-Ohm are the most common varieties. The output of an RTD is much more linear in comparison to thermistors, and thermocouples. Also, platinum RTD resistance vs. temperature is very stable and reproducible.
RTD construction is a delicate process and fabricating an RTD to minimize impurities and deformation is extremely important. The construction of an RTD determines whether it is a class A, B, C RTD element. A proper RTD design and careful material selection will minimize the effects of impurities (thermocouple effect) and deformations (strain and symmetry effects) such that an RTD’s resistance only varies with temperature.
Sensor assemblies can be categorized into two groups by how they are installed or interface with the process: immersion or surface mounted.
Immersion sensors take the form of an SS tube and some type of process connection fitting. They are installed into the process with sufficient immersion length to ensure good contact with the process medium and reduce external influences. A variation of this style includes a separate thermowell that provides additional protection for the sensor. These styles are used to measure fluid or gas temperatures in pipes and tanks. Most sensors have the sensing element located at the tip of the stainless steel tube. An averaging style RTD however, can measure an average temperature of air in a large duct. This style of immersion RTD has the sensing element distributed along the entire probe length and provides an average temperature. Lengths range from 3 to 60 feet.
Surface mounted sensors are used when immersion into a process fluid is not possible due to configuration of the piping or tank, or the fluid properties may not allow an immersion style sensor. Configurations range from tiny cylinders to large blocks which are mounted by clamps, adhesives, or bolted into place. Most require the addition of insulation to isolate them from cooling or heating affects of the ambient conditions to insure accuracy.
Other applications may require special water proofing or pressure seals. A heavy-duty underwater temperature sensor is designed for complete submersion under rivers, cooling ponds, or sewers. Steam autoclaves require a sensor that is sealed from intrusion by steam during the vacuum cycle process.
Immersion sensors generally have the best measurement accuracy because they are in direct contact with the process fluid. Surface mounted sensors are measuring the pipe surface as a close approximation of the internal process fluid.
Pressure sensors are most commonly built from strain gages. The strain gage is essentially a resistive Wheatstone bridge network bonded onto a rigid substrate. When a force/pressure is applied on the gage, the resulting deformation causes the resistance of the bridge network to change, and thus upsets the balance of the Wheatstone bridge. This produces an output voltage, proportional to the resistance change which in turn is a measure of applied pressure/force. Similar strain gages could also be constructed from a capacitive Wheatstone bridge network.
P α (Vout) α R
R= ρ (L/A)
P: Applied Pressure
Vout: Bridge output voltage
ρ: Resistivity of resistive element
L: Length of resistive element
A: Area of cross-section of resistive element
Pressure Sensor Terminology
Offset is the output of the sensor without any applied stimulus. For an ideal bridge all the resistance elements would be exactly matched and the offset would be zero. In reality, the offset can a significant percentage of the sensors full scale output (FSO). A typical offset of 15 percent is common for many sensor types.
The span of a sensor is defined as the difference between the full scale output and the offset (Span =FSO- offset). The span and offset of these sensors is typically a small dc voltage. For common pressure sensors, spans can range from 1mV per volt Volt to 20mV per Volt (5mV to 100mV with a 5Vexcitation).
Pressure Sensor Design
The design of most sensor systems involves understanding the sensor characteristics, choosing a topology, and determining the system output targets specifications. Normally a great part of the designer’s time is spent selecting component values and making circuit design changes to meat the system design targets.
In the case of the PGA309 and PGA308, Texas Instruments provides the basic circuit topology for the most common customer requirements. Typically these topologies can be used with only minor value changes. The main adjustments required for signal conditioning bridge sensors are done automatically during calibration. For example, the PGA309 gain, offset, temperature drift correction, and linearity correction are automatically adjusted during calibration by the software. No knowledge of sensor characteristics is required to make the calibration adjustments. The span, offset, and drift of the sensor is automatically determined during calibration.
The application requirements of flow measurement in industrial settings varies from low cost to very high precision and fast flow metering found in petrochemical and pharmaceutical plants. The two main methods are Magnetic-Inductive and the Coriolis Flow Meter.
The Electromagnetic Flowmeter consists of a non-ferromagnetic tube wrapped with a magnetic coil. Electrodes in the tube’s inner isolated surface are in contact with the liquid (must be conductive) that flows through the tube. The coils around the pipe generate a magnetic field within the tube. The magnetic field inducts a voltage in the liquid, which is proportional to the speed of the liquid in the tube. This voltage is measured via the electrodes. As the measured voltage is very low, precise low-noise signal conditioning is required.
Coriolis Flowmeter is a popular Flowmeter that directly measures mass flow rate. The pipe through which the fluid is flowing is made to oscillate at a particular resonant frequency by forcing a strong magnetic field on the pipe. When the fluid starts flowing through the pipe, it is subject to Coriolis force. The oscillatory motion of the pipe superimposes on the linear motion of the fluid exerting twisting forces on the pipe. This twisting is due to Coriolis acceleration acting in opposite directions on either side of the pipe and the fluids resistance to the vertical motion. Sensor electrodes are placed on both the inlet and outlet sides which pick up the time difference caused by this motion. This phase shift due to the twisting forces is a direct measurement of mass flow rate.
Low noise instrumentation amplifiers followed by precision ADC is typical of the signal chain path. TI’s high resolution differential ADCs have low power consumption, wide dynamic range and low noise. This can be used to digitize the analog output for high resolution, precision measurements. Multiple channel ADCs with simultaneous sampling architectures enable taking multiple measurements such as temperature, phase, density etc in one shot.
Further calibration routines and algorithms can be run on the ultra low-power MSP430. If more signal processing power is required, one could use the DSP core from TI. The low power DSP cores from TI have a FFT accelerator core that enables computing FFTs in a matter of seconds while drawing very little current. The ultra-low power architecture of the DSP offers superior signal processing power while still being able to be powered off the 4-20mA loop.
Signal Acquisition and Processing
A pH electrode measures hydrogen ion (H+) activity and produces an electrical potential or voltage. The operation of the pH electrode is based on the principle that an electric potential develops when two liquids of different pH come into contact at opposite sides of a thin glass membrane. The modern pH electrode is a combination electrode composed of two main parts, a glass electrode and a reference electrode. pH is determined essentially by measuring the voltage difference between these two electrodes. At the tip of the electrode is the thin membrane which is a specific type of glass that is capable of ion exchange. It is this element that senses the hydrogen ion concentration of the test solution. The reference electrode potential is constant and is produced by the reference electrode internal element in contact with the reference-fill solution which is kept at a pH of seven.
Electrochemical sensors are widely used as a sense mechanism for gas and chemical sensing. Common applications include carbon monoxide detectors, chemical species identification, Amperometric sensors etc. Electrochemical sensors can be considered simply as transducers that convert the physical characteristic of gas/chemical concentration to an electrical signal which can be processed by instrumentation.
The programmable Analog Front End (AFE) is perfect for use in micro-power electrochemical sensing applications. It provides a complete signal path solution between a sensor and a microcontroller that generates an output voltage proportional to the cell current. The programmability enables it to support multiple electrochemical sensors such as 3-lead toxic gas sensors and 2-lead galvanic cell sensors with a single design as opposed to the multiple discrete solutions. The AFE supports gas sensitivities over a range of 0.5 nA/ppm to 9500 nA/ppm. It also allows for an easy conversion of current ranges from 5µA to 750µA full scale. The adjustable cell bias and Transimpedance amplifier (TIA) gain are programmable through the I2C interface. The I2C interface can also be used for sensor diagnostics. An integrated temperature sensor can be read by the user through the VOUT pin and used to provide additional signal correction in the µC or monitored to verify temperature conditions at the sensor. The AFE is optimized for micro-power applications and operates over a voltage range of 2.7V to 5.25V. The total current consumption can be less than 10μA. Further power savings are possible by switching off the TIA amplifier and shorting the reference electrode to the working electrode with an internal switch.
TI's high resolution differential ADCs have low power consumption, wide dynamic range and low noise. This can be used to digitize the conditioned analog bridge output for high resolution, precision measurements. Alternately, one could use TI's MSP430 microcontrollers with integrated ADCs and DACs. Further post processing algorithms can be run on this MCU.
Signal Acquisition and Processing