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Product List

T.M.I.

Test and Measurement Instruments C.C.

CK 1985/007464/23

“Tomorrow’s Instruments Today” — “For Good Measure” ^®

TMI, Established—1982

English, Afrikaans, Portuguese Speaking. Master/Visa Credit Cards

Pressure / Vacuum Meters

Pressure, Vacuum

Part No: PS-9302

Pressure / Vacuum, Needs Sensor - 2,5,10,20,50,100 or 400 Bar Sensor, PSI, Kg/cm3,inch/Hg, Memory, Data-Hold & RS232 Serial Interface, Zero Button

Part No: VC-9200

Vacuum / Pressure, 1 to 1500mbar(2000mbar Max), Separate probe, 8 Display Units, data-hold, Record-Max/Min, RS232

Lutron

Accessories

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Part No: PS-100xxBAR

Pressure Sensor for PS9302, 2,5,10,20 or 50 Bar Sensor

Lutron

Part No: PS100100BAR

Pressure Sensor for PS9302, 100 Bar Sensor

Lutron

Part No: PS100400BAR

Pressure Sensor for PS9302, 400 Bar Sensor

Lutron

Part No: PS-403

Pressure / Vacuum Adaptor, Pressure: 0.5 to 500PSI, 3,447 to 3447Kpa, Vacuum: 0 to 29,99in-Hg, 0 to 76cm-Hg. For Use with Digital Multimeters.

Lutron

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Notes on Pressure and Vacuum Meters.

Pressure instruments can be used to measure, monitor, record, transmit or control pressure and vacuum. There are several types of devices. Recorders are used to measure values or accumulate totals. Controllers can be used to regulate positive or negative (vacuum) pressure. They receive sensor inputs, provide control functions, and output control signals. Some pressure instruments are self-contained devices that provide an output such as a display. Analog meters use a simple visual indicator such as a dial. Digital displays present numeric or application-specific values with LCD or LED displays. Cathode ray tubes (CRT), now very outdated, and other multi-line displays are also available. Some pressure instruments are suitable for measuring the pressure and vacuum of liquids or gases. Others are rated in hazardous applications. Import specifications to consider include working pressure or vacuum range, accuracy, and operating temperature. Temperature outputs, temperature compensation, negative pressure outputs, alarm indicators, and transistor-transistor logic (TTL) switches are commonly offered as a package.

Pressure and vacuum instruments use many different sensing technologies. Mechanical deflection devices such as diaphragms, Bourdon tubes or bellows consist of an elastic or flexible element that is deflected mechanically by a change in pressure. Sealed pistons or cylinders are also available. Strain gauges are bonded to a larger structure that deforms as pressure or vacuum changes. Piezoresistive devices sense shifts of electrical charges within a resistor. Piezoelectric pressure and vacuum instruments measure dynamic and quasi-static pressures and vacuums. Their common modes of operation are charge mode, which generates a high-impedance charge output; and voltage mode, which uses an amplifier to convert the high-impedance charge into a low-impedance output voltage. Thin film devices consist of an extremely thin layer of material, usually titanium nitride or polysilicon, deposited on a substrate. Pressure and vacuum instruments that use microelectromechanical systems (MEMS), variable capacitance, and vibrating elements are commonly found in the market.

Pressure and vacuum instruments are capable of performing various pressure and vacuum measurements and displaying amounts in different units. Absolute pressure is a pressure measurement that is relative to a perfect vacuum. Typically, vacuum pressures are lower than the atmospheric pressure. Gauge pressure, the most common type of pressure measurement, is relative to the local atmospheric pressure. By contrast, sealed gauge pressure is relative to one atmosphere of pressure (oz) at sea level. Differential pressure reflects the difference between two input pressures. Compound pressure instruments can display both positive and negative pressures. Some pressure instruments display values in pounds per square inch (PSI), kilo pascals, bars or millibars, inches or centimeters of mercury, or inches or feet of water. Other devices display measurements in ounces per square inch or kilograms per square centimeter.

Pressure and vacuum instruments can produce several types of electrical signals, including analog voltage and analog current. These output signals can be encoded via amplitude modulation (AM), frequency modulation (FM), or some other modulation scheme such as sine wave or pulse train. Common communication protocols include Ethernet, DeviceNet, FOUNDATION Fieldbus, and highway addressable remote transmission (HART^Ò). HART is a registered trademark of the HART Communication Foundation. Several serial and parallel interfaces for pressure instruments are available. RS232 and RS485 are serial, digital protocols. Parallel protocols include the general-purpose interface bus (GPIB), a standard which is also known as IEEE 488. Some pressure instruments output TTL signals. Others provide outputs that change the state of a switch or alarm.

Notes on Vacuum gauges.

Vacuum gauges are devices for measuring vacuum or sub-atmospheric pressures. They use several different technologies. Manometers are usually made of a transparent U-shaped tube and partially filled with a liquid such as water, mercury or oil. The relative amount of liquid displacement between the legs of the U indicates the excess of pressure exerted on one side or the other. Thermocouple gauges measure changes in the thermal conductivity of a residual gas within a gauge tube. These devices include a filament, power supply for the filament, and moving coil meter for displaying the pressure. Hot cathode ionization gauges initiate a constant electron flow from the cathode or electron source to the anode or electron drain. These electrons hit a pressure-dependent quantity of gas molecules, which become positive ions and cause a pressure-related current on the ion collector. Cold cathode ionization gauges are also available. Because they do not have active components such as hot filaments, cold cathode gauges can withstand sudden or prolonged exposure to high-pressure gases.

Selecting vacuum gauges requires an analysis of display types, scale types and scale units. Some devices include analog or digital meters. Others include a cathode ray tube (CRT), liquid crystal display (LCD), or other multi-line video display. Single scale devices display pressure in only one set of units. By contrast, dual scales devices display pressure in two sets of units on the same dial face. There are many scale units for vacuum gauges. Examples include pounds per square inch (psi), kilo pascals (kPa), atmospheres (atm), bars, inches of mercury (inHg), centimeters of mercury (cmHg), inches of water (inH₂O), feet of water (ftH₂O), kilograms per square centimeters (kg / cm²), and ounces per square inch (oz / in²).

Specifications for vacuum gauges include vacuum range, operating temperature, accuracy, and media. Accuracy, the difference between the true value and the indication expressed as a percentage of the span, includes the combined effects of method, observer, apparatus and environment. Typically, vacuum gauges use accuracy grades from the American Society of Mechanical Engineers (ASME) and Deutsches Institut für Normung (DIN), a German national organization for standardization. Examples include grades A, B, C, and D as well as grade 1A (1% full scale), 2A (0.5% full scale), 3A (0.25% full scale), and 4A (0.1% full scale). Some vacuum gauges measure the pressures of liquids. Others measure the pressures of solids. Devices that are rated for hazardous duty or for unlisted, specialized or proprietary materials are also available.

Vacuum gauges are available with a variety of features, signal outputs, and communication protocols. Some devices include temperature measurement outputs or temperature compensation to prevent measurement errors due to changes in temperature. Other devices include audible or visual alarms, or an output switch that is compatible with transistor-transistor logic (TTL). Typically, the output voltage is a linear function of the measurement. Analog current is imposed on the output circuit proportional to the measurement. Serial interfaces for vacuum gauges include RS232 and RS485. Parallel interfaces are also available. Other communication protocols include DeviceNet, Fieldbus, Ethernet, and PROFIBUS.