Test & Measurement

Analog Signal Conditioning for Accurate Measurements

By Jon Titus Q: Should I put some sort of circuit between my sensor and an analog-to-digital converter? A:Yes. You probably need some signal conditioning. The explanation below goes on for a bit, but stay with it and you'll understand what you need and why you need it. Before you make any connections, get the electrical specifications for the analog-to-digital converter (ADC) and for the sensor or sensors in your system. Let's assume the data-acquisition module uses a Maxim Integrated Products MAX197 12-bit ADC. This device can accept eight differential (2-wire) inputs or 16 single-ended (1-wire) inputs. Maxim's specifications show an input impedance of 21 kohms for single-ended inputs and 16 kohms for differential inputs.

Posted in: White Papers


Process-Hardened, Multi-Analyte Sensor for Characterizing Multiple Rocket Plume Constituents in a Test Environment

A multi-analyte measurement capability is integrated into a single sensor. Stennis Space Center, Mississippi Stennis Space Center (SSC) is one of three government-operated rocket engine test facilities in the United States and is the primary center for testing and flight-certifying rocket propulsion systems for future space vehicles. Safety is a top priority at NASA-SSC. To safely test and certify rocket engines, monitoring technologies for rocket test stands, which (1) verify compliance with federal, state, and local government guidelines; (2) ensure a safe work environment for its personnel at ground testing facilities; as well as (3) monitor environmental impacts, are all required. Additionally, NASA has a need to monitor engine combustion efficiencies and engine health of a variety of launch vehicle configurations utilizing liquid oxygen, liquid hydrogen, isopropanol, and kerosene. Multi-analyte measurement technology is essential for a safe and effective working environment. Therefore, for the advancement in multi-analyte technology in the rocket testing industry, a device was created that integrates multi-analyte measurements into a single sensor unit.

Posted in: Articles, Briefs, Sensors, Monitoring


Automated Table Lookup Solution Algorithm of the Optimal Powered Descent Guidance for Planetary Landing

NASA’s Jet Propulsion Laboratory, Pasadena, California A novel automated table lookup method is developed to compute the near-fuel-optimal powered descent guidance trajectories, in real-time, for planetary soft landing. The main advantage of this algorithm is that it can be executed autonomously in milliseconds without performing iterative numerical computations to obtain the solution of the optimization problem. The key enabling idea behind this approach is to store, in a lookup table, a number of optimal trajectories that have been computed on the ground for a systematically chosen set of initial conditions. In flight, a near-fuel-optimal trajectory is computed for the actual initial condition by interpolating between these pre-computed trajectories. The lookup method requires only a small, predetermined number of basic algebraic operations. Moreover, this method guarantees that the interpolated solutions are in a prescribed neighborhood of the true optimal solutions.

Posted in: Articles, Briefs, Aviation


Computation of Wing Deflection and Slope from Measured Strain

Patent-pending methodology computes detailed wing loads during actual flight. Armstrong Flight Research Center, Edwards, California A lightweight, robust fiber-optic system is the technology behind a new method to compute wing deflection and slope from measured strain of an aircraft. This state-of-the-art sensor system is small, easy to install, and fast, and offers the first-ever means of obtaining real-time strain measurements that can accurately determine wing deflection and slope during flight. Such measurements are particularly useful for real-time virtual displays of wing motion, aircraft structural integrity monitoring, active drag reduction, active flexible motion control, and active loads alleviation.

Posted in: Articles, Briefs, Aviation, Measuring Instruments


A Continuous-Flow, Microfluidic, Microwave-Assisted Chemical Reactor

The reactor uses a directed 60-GHz source, which may require far less power to observe the same reactivity profiles. NASA’s Jet Propulsion Laboratory, Pasadena, California In industrial synthetic chemistry laboratories, reactions are generally carried out using batch-mode methodologies, stepwise reactions, and purifications to generate a final product. Each step has an associated yield of both the reaction itself and of the final purification that is largely dependent on the procedure being used, and the scientist carrying out the procedure. Continuous-flow reactors are one way of streamlining the process. Furthermore, microwave-enhanced, or microwave-assisted, chemistry has been demonstrated to aid in many of these areas; however, scaling has been a traditional problem with this technique.

Posted in: Articles, Briefs, TSP


High-Resolution Data Acquisition System Enables Reliable Engine Parameter Measurements

Obtaining accurate measurements is critical for improving vehicle component performance and overall system reliability. HBM, Inc., Marlborough, Massachusetts Data acquisition plays a critical role in improving vehicle component performance and overall system reliability. Measuring engine parameters, including engine cranking speed and the mechanical condition of the engine, requires high-resolution data acquisition equipment.

Posted in: Articles, Briefs, Data Acquisition, Measuring Instruments


Guarded Flat Plate Insulation Test Cryostat

Features include high testing rate and high data quality. John F. Kennedy Space Center, Florida The guarded flat plate insulation test cryostat (Cryostat-500) is a boil-off calorimeter comprising a flat-bottom test apparatus for measuring the absolute thermal performance of an insulation test article. Typical dimensions allow accepting test specimens 200 mm in diameter by up to 30 mm thick. The test chamber is guarded by a second cryogen chamber to prevent parasitic heat loads. System insulation materials provide additional thermal stability for testing over a wide range of environmental conditions. The cold-mass assembly can be configured for rigid or soft materials, with or without compressive loads.

Posted in: Articles, Briefs, Data Acquisition