Abstract: A fluid flow direction and velocity monitor, particularly useful in monitoring pressure differentials between a controlled environment and its surroundings, includes a heated thermal sensor situated between upstream and downstream cold thermal sensors within a channel. The heated thermal sensor provides a pressure differential or fluid flow velocity signal. The pair of cold thermal sensors are utilized to provide both temperature compensation and fluid flow direction. The pressure differential and direction signals are combined by the circuitry to yield a single digital direction and pressure signal.

Abstract: A fluid flow detection monitor (80), particularly useful in monitoring pressure differentials between a controlled environment and its surroundings, includes a heat source (1) situated between an upstream and downstream thermal sensor (2,3) within a channel (5). The electrical resistance of the downstream sensor varies as the downstream sensor is heated from fluid carried past the heat source. Circuitry is used to detect the electrical resistance differential between the thermal sensors, thereby detecting the presence of fluid flow.

Abstract: A modular metering instrument including one of a plurality of sensing probes or probe modules including identification and calibration information stored therein and a meter module which can identify the sensing probe when the sensing probe is connected thereto. The storage of calibration and identification information in the sensing probe allows the meter module to be utilized with any one of a number of sensing probes to sense different physical parameters. The sensing probe includes at least one sensor and related circuitry to generate a signal relating to the sensed parameter. The meter module analyzes and calibrates the signal and displays the measured parameter.

Abstract: A temperature compensated air flow monitor which measures true flow velocity or volume flow. The air flow monitor can be mounted in or coupled to a fume hood and includes a fluid flow tube having a pair of thermistors mounted therein. A first cold thermistor is utilized to provide temperature compensation to the second hot thermistor which provides the fluid flow velocity measurement. The pair of thermistors can be mounted to or in a probe for a portable air flow monitor application. The measured flow velocity or volume flow can be utilized in a display for the operator and also can activate one or more alarms when the flow velocity varies from a desired range.

Abstract: An improved selector provides for air paths between a meter and an air volume sensing manifold that are similar for both up and down flow of air through the apparatus thereof. This provides similar momentum losses in the air reaching the meter for both air up and down flow through the apparatus to obtain more accurate meter readings of the air flow volume. Separate throttling screws are provided for the throttling orifices, providing different range selections, and are independently adjusted to compensate for minor air passage differences in the selector, and air flow pattern differences in up and down flow. A calibrated area reducer in the form of a sheet of perforated stock is positioned upstream in the throat in contact with the manifold to extend the measuring range of the apparatus while minimally disturbing the air flow patterns through the apparatus.

Abstract: A diesel engine monitor monitors the exhaust gas temperature of each cylinder. A thermocouple is coupled to each cylinder and the monitor scans the analog signal output from each thermocouple which is proportional to the engine exhaust temperature of the cylinder. The analog temperature signal is digitized and stored. A microcomputer controls the operation of the monitor and reads each individual temperature after it has been stored. The microcomputer averages the last temperature stored from each cylinder to form a total moving average for the engine which moves as each engine cylinder exhaust temperature is rescanned. The monitor first checks to see if the temperature signal from a cylinder is due to an open thermocouple. The microcomputer then compares the latest temperature to the previous temperature for that cylinder to determine if it has changed more than 100 degrees.