Frequently Asked Questions

• Can I order gauges with my own logo? Yes. Marshall Instruments specializes in custom gauges. Minimum order of 100 units typically applies. Contact us for a quote.

• What is the screw in the connection for? This is a restrictor screw (removable) for pulsation dampening.

• What is your minimum order? Minimum opening order is typically $300. Minimum reorder is $200.

• What is the warranty on 1-1/2" gauges? We have a 1 Year warranty against manufacturer defects. Misuse and/or abuse is not covered under the warranty. Proof of purchase is required.

  If you did not purchase your product from Marshall Instruments, please check with the retailer/distributor you purchased from as the each have their own return/exchange policies.

  If you are having a problem please contact us so that we can help.

• How Does Temperature Affect A Filled Gauge? Changes in ambient temperature affects the accuracy of gauges in several ways.

  Range Shift
  Range shift is caused by the change in modulus of elasticity of the bourdon. This effect increases proportionately as the pressure increases. As a general rule, the loss of accuracy will be an additional 1% of full scale reading for every 50 degree F change in temperature.

  Zero Shift
  Zero shift is created by the change in physical dimensions of the various components brought about by the temperature change. This shift is constant over the entire scale and does not vary with applied pressure.

  Maximum Temperature Limits
  To ensure longest, possible life and accurate readings, pressure gauges that have soft-soldered pressure joints should not be exposed to process or ambient temperatures over 120 degree F. This is especially true of pressure gauges with liquid filled cases, due to the expansion of the case fill fluid. Long term exposure to temperatures in excess of 120 degree F may cause discoloration of dials and fill fluids, as well as hardening of the case seals and possible fill leakage. Gauges with silver soldered or welded pressure joints should not be exposed to process or ambient temperatures over 190 degree F.

• What is the Accuracy? Our gauges have an accuracy of 2% at mid scale. High and low temperatures affect accuracy on indication. A general rule of thumb for dry gauges is 1% of full scale change for every 50 degree F change from 75 degree F. Double that allowance for gauges with liquid filled cases.

• About Marshall Thermometers Marshall thermometers are designed for Industrial and Laboratory applications. We can fabricate to your specifications. A choice of Fahrenheit, Centigrade, and dual ranges are available in 1", 1 1/2", 2 1/4", 3" and 5" dial sizes with stem lengths from 2 1/2" to 84". For custom dials and special mountings - our Engineering Department is at your service.

• Centigrade Ranges Available Download PDF document showing Centigrade/Celcius ranges available.

  Ranges Available (PDF)

• Dual Ranges (F/C) Available Download PDF document showing dual F/C ranges available.

  Ranges Available (PDF)

• Fahrenheit Ranges Available Download PDF document showing Fahrenheit ranges available.

  Ranges Available (PDF)

• Guarantee If there is evidence of defective materials or workmanship in any Marshall thermometer it will be repaired or replaced without charge. It must be sent, prepaid, to our factory within one year from date of shipment.

• Shipment and Terms Marshall Instruments, Inc. offers immediate delivery. Terms are 30 days F.O.B. Anaheim, CA 92806.

• Corrosion Resistance Marshall thermometers are fabricated with type 303 and 304 stainless steel and are corrosion resistant to most acids and gases. All parts of the Marshall thermometer are protected from corrosion by nickel, plating or by use of silver solder. Many corrosive conditions can be overcome by coating the stem with plastic or by the use of separate sockets. It is necessary to state all particulars before recommendations can be made.

• Accuracy Marshall thermometers are accurate to within one percent of the scale range and can be calibrated to your requirements. The over range protection is 50 percent up to 500 DEGF and 10 percent above 500 DEGF.

• Dials Marshall thermometer pointers are non-magnetic and are designed to relative width of dial increments for fractional reading. Silicon damping is used to eliminate excessive vibration. The dial mountings prevent excessive heat transfer and eliminate discoloration. The dials are buffed, anodized and etched, with black enamel filled increments for easy reading.

• Special Type Adaptations Our urn type thermometer is ideal for coffee and hot chocolate urns, roll warmers, steam tables and ovens. A sturdy aluminum handle added to a Model B thermometer with a spiked stem is ideal for testing soil, asphalt, and other penetrable materials.

• Safety and Reliability McDaniel Controls, Inc., designs and manufactures its gauges to minimize failure and to protect personnel and property. The use of laminated safety glass, rather than plexiglass or singlestrength glass, prevents dangerous pressure build-up in the case; the glass breaks at pressures that vary with the glass diameter. The brittle glass cracks uniformly and the laminate glass won't craze or discolor in service.

• Easy Repair If any McDaniel gauge requires repair, down-time can be minimal because all McDaniel gauges are field-repairable, quickly and easily, with only a screwdriver needed for disassembly. If circumstances permit and factory repair is preferred, we will make that repair at a nominal service charge. See Warranty and Repair for further details.

• Pulse Vibration Protection McDaniels offers liquid-filled gauges for applications involving vibration or pulsation. Glycerin is an excellent damper of Bourdon tube movement. Emersion of the entire measuring assembly in a protective liquid envelope provides lubrication and shuts out corrosive or dirty atmospheres - thereby minimizing wear of moving parts and prolonging gauge life significantly.

• Choice of Filling When you order a McDaniel Filled Gauge you may choose to fill it yourself or you may order it factory filled with the liquid of your choice. Thus, you can maximize inventory utility and minimize inventory cost. Glycerin filling has a lower operating temperature limit of 32 DEGF undiluted. The mixture of distilled water in proportions up to 35% will lower the limit commensurately, to -40 DEGF.

  Silicone can extend the lower temperature limit to -60 DEGF. The maximum temperature limit is not determined by the fluid but by the gauge's synthetic case seal. At elevated temperatures the seal may bake and loose its elasticity.

  Warning: Glycerin filled gauges should not be used in applications involving strong oxidizing agents such as chlorine, nitric acid or hydrogen peroxide.

• Warranty and Repair We warrant our pressure gauges to be free of defects in material and workmanship:

  Replacementof any defective gauge will be made at no cost to the purchaser. We will repair any of our gauges which has malfunctioned for a cost of $15.00 on 4" and larger sizes; $7.50 on 2-1/2" and smaller. Prices are F.O.B. Paradis, Louisiana.

• How Does a Mechanical Gauge Work? Mechanical gauges utilize an internal bourdon tube. One end of the bourdon tube is connected to a gear and shaft assembly that moves a pointer. When the pressure inside the bourdon tube increases, the bourdon tube uncoils slightly. The amount of uncoiling that occurs is proportional to the pressure inside the bourdon tube. As the tube uncoils, its motion activates the gear and shaft system that turns the pointer on the gauge. While all that you see when you look at the gauge is the pointer moving, you should understand that there is a small, bent tube (the bourdon tube) that's coiling and uncoiling with each change in the pressure inside that tube.

  
  

  Mechanical pressure gauges are connected directly to the process fluid being measured (i.e. oil). As the process fluid pressure changes the pressure on the bourdon tube also changes which in turn moves the pointer on the gauge.

  Mechanical temperature gauges also utilize a bourdon tube. They have a sealed capillary tube and bulb assembly that is filled with temperature sensitive liquid that produces a proportional vapor pressure on the bourdon tube. As the temperature changes, the pressure inside the bourdon tube changes, which in turn moves the pointer on the gauge.

• How Does an Electric Gauge Work? The Marshall Comp II short sweep voltmeter works via deflection of the pointer from a magnetic field that is directly proportional to the voltage being measured. The magnetic field is generated by a tightly wound coil. An increase or decrease in voltage through the coil creates a corresponding change in the magnetic field, which in turn moves the pointer.

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