UNIVERSAL CALIBRATING MACHINES

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Derrick Francis
5 years ago
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1 FIGURE 1-100,000 lbf Morehouse Universal Calibrating Machine using a Morehouse Proving Ring to calibrate a Load Cell in compression. An optional Auxiliary Screw Pump is attached to Machine s upper platen. Force measurement instrumentation must be calibrated at regular intervals to ensure their accuracy. Accurate force calibration improves quality, increases production yields, assures consistency, improves safety, and ensures measurements are compatible with those made elsewhere. To ensure proper calibration and the accuracy of force measurement instrumentation such as Load Cells, Proving Rings, Force Gauges, Crane Scales, Traction Dynamometers, and other load sensing elements Morehouse manufactures the Universal Calibrating Machine. The Morehouse Universal Calibrating Machine is a versatile machine in which the calibration standard, such as a Morehouse Proving Ring or Morehouse Load Cell, and the unit under test (instrument to be calibrated) are positioned in the machine and loaded in series with a mechanical force. The force is produced by a hydraulic jack activated by a precision, manually operated, two-speed hand pump especially designed for calibration work. An Auxiliary Screw Pump (sold separately) and Hydraulic Power Control (sold separately) are available for use with most Morehouse Universal Calibrating Machines. The Morehouse Universal Calibrating Machine facilitates calibration in both compression and tension. It is available in many different capacities from 10,000 lbf [50,000N] to 2,250,000 lbf [10,000,000 N]. Special capacities are designed and manufactured to order. The Morehouse Universal Calibrating Machine is designed to use a compression force standard, Morehouse Proving Ring or Morehouse Load Cell, to calibrate units under test in either compression or tension. This results in substantial cost savings as the expense of maintaining a tension and compression force standard is eliminated. The Morehouse Universal Calibrating Machine provides for the calibration of the unit under test in accordance with standards such as ASTM E74, ISO 376, and other industrial and government specifications.

CONSTRUCTION The Morehouse Universal Calibrating Machine consists primarily of three major parts - the stationary frame, the movable frame or yoke, and the hydraulic jack (see FIGURE 2).

Friction between the calibration standard (Proving Ring or Load Cell) and the unit under test has been completely eliminated.

2 CONSTRUCTION The Morehouse Universal Calibrating Machine consists primarily of three major parts - the stationary frame, the movable frame or yoke, and the hydraulic jack (see FIGURE 2). While a Proving Ring or Load Cell is essential to the function of calibration, they are not supplied as part of the machine. The entire design of the machine has one purpose - ultimate accuracy. Friction between the calibration standard (Proving Ring or Load Cell) and the unit under test has been completely eliminated. This is essential as even slight friction found in some types of calibrating machines results in gross inaccuracies. Non-axial loading, another factor contributing to inaccurate calibrations, is eliminated by the design of the machine and its accessories and adaptors. The lower platen of the stationary frame and the lower yoke have center holes. These holes provide a means by which an instrument to be calibrated in tension can be attached to the machine with suitable studs or tension members. Machines with capacities of 200,000 lbf and less have a ball seat adaptor in the upper yoke. The ball seat adapter assures axial loading by allowing a hardened steel ball to be positioned between the upper yoke and the Proving Ring or Load Cell being used as the force standard. The upper yoke is adjustable to allow for instruments of varying heights and to facilitate lifting the yoke during calibration setups. The hydraulic jack is activated by a pump. The pump is connected to the jack by a hydraulic hose with a quick disconnect. Dimensional data on Morehouse Universal Calibrating Machines of standard capacities are tabulated on the accompanying drawings. FIGURE 2-60,000 lbf machine showing (A) adjusting motor, (B) hydraulic jack, (C) upper machine platen, (D) upper yoke, (E) lower yoke, and (F) lower machine platen APPLICATION FIGURE 3 - Suggested compression calibrating setup for all capacity machines FIGURE 4 - Suggested tension calibrating setup for all capacity machines FIGURE 5 - Suggested tension calibrating setup for digital dynomometers The Morehouse Universal Calibrating Machine may be used wherever it is necessary to apply an accurate mechanical force. It is designed to accommodate various instruments that require calibration including Load Cells, Proving Rings, Force Gauges, Crane Scales, Traction Dynamometers, and other load sensing elements used in weighing and force calibration In a standard compression calibration the calibration standard, Morehouse Proving Ring or Load Cell, is positioned between the jack and the upper yoke. The unit under test is placed between the upper machine platen and the lower yoke. (See FIGURE 3) In a tension calibration the setup of the calibration standard is the same. The unit under test is connected between the lower yoke and the lower platen by suitable tension members. The tension calibration setups show a load cell standard used to calibrate another load cell in tension (See FIGURE 4) and an electronic dynamometer (See FiIGURE 5).

Selection of a location where an even temperature prevails will facilitate the calibration.

3 SET UP FOR CALIBRATION The set up of the Morehouse Universal Calibrating Machine for calibration is best described in two steps. Positioning the force standard, Morehouse Proving Ring or Load Cell, and positioning the unit under test. Prior to use, the machine should be set on a solid surface and leveled by adjusting the feet. Selection of a location where an even temperature prevails will facilitate the calibration. POSITION THE FORCE STANDARD The force standard, Morehouse Proving Ring or Load Cell, is positioned the same for calibrating the unit under test in either compression or tension. To position the force standard, raise the upper yoke and place the force standard on the jack. To raise the upper yoke, the lock collars on the yoke tie bars are placed against the top side of the upper platen and locked there FIGURE 6- (A) upper yoke; (B) load ball by the set screws. With adaptor; (C) upper boss of proving ring; (D) proving ring; (E) alignment bushing; (F) jack ram the yoke thus suspended, the upper yoke is raised by operating the motor until there is enough space to insert the force standard. Lower the upper yoke until the ball seat adaptor or other adaptor in the upper yoke rests on the ball or top of the force standard. To assure proper alignment and axial loading it is advisable to use the accessories and adaptors shown in FIGURE 6 when positioning Proving Rings and those shown in FIGURE 7 when positioning Load Cells. With the force standard in FIGURE 7 - (A) upper yoke; (B) load ball adaptor; (C) ball clip adaptor; (D) load cell; (E) alignment plug; (F) alignment adaptor; (G) jack ram. place and the yoke lowered to rest on the loading ball, release the lock collars. POSITION THE UNIT UNDER TEST COMPRESSION: Measure the distance between the upper machine platen and lower yoke. This distance should be approximately the height of the unit under test plus any adaptors being used. If it is not, raise or lower the yoke. Mount the unit under test. Load cells or other instruments having a tapped central hole in their base should be mounted using an alignment plug and load cell adaptor plate to assure location of the load cell on the loading axis of the machine. Load cells with a circle of tapped mounting holes in their base are first mounted to a load cell adaptor plate, which, in turn, is mounted to the lower machine platen. Be sure the adaptor plate is counter bored so that all the bolt heads will be completely recessed. FIGURE 8 - (A) upper platen; (B) threaded alignment bearing block; (C) spherical load button; (D) load cell; (E) load cell alignment plug; (F) load cell adaptor plate; (G) lower yoke. TENSION: Preparation for a tension calibration is much the same as that of a compression setup. The only difference is the manner in which the unit under test is mounted in the machine. For a tension calibration, the unit under test is suspended between the lower yoke and the lower machine platen by tension member. These tension members will usually have spherical connections at both ends to assure axial loading. Tension FIGURE 9 - (A) lower yoke; (B) tension member; (C) load cell. members are available from Morehouse.

4 TYPICAL MOREHOUSE CALIBRATING MACHINE SET UPS FOR CALIBRATION With the many different types of instruments than can be calibrated using the Morehouse Universal Calibrating Machine there are many accessories and adaptors for mounting them. Bulletin 271 illustrates many of these accessories and adaptors. Please call, write, or visit our website ( for a copy of Bulletin 271. If the accessories or adaptors required are not listed in this Bulletin please contact us to discuss your requirements. The following figures exemplify some typical calibration set ups using the recommended accessories and adaptors:

under the test are available. Pictured here is a 60,000 lbf Morehouse Universal Calibrating Machine set up to calibrate a load cell in compression.

5 MOREHOUSE COMPLETE CALIBRATION SYSTEM WITH COMPUTER INTERFACE Morehouse Instrument Company can provide a complete calibration system. Proving Rings and Load Cells are offered for use as calibration standards with the Morehouse Universal Calibrating Machine and mounting accessories and adaptors for both the force standard and unit under the test are available. Pictured here is a 60,000 lbf Morehouse Universal Calibrating Machine set up to calibrate a load cell in compression. The machine is shown with the standard hand pump and optional Auxiliary Screw Pump. A Morehouse Ultra Precision Calibration Standard Load with a Morehouse Model 4215 Load Cell Indicator is being used as the force standard. A laptop computer uses software developed by Morehouse to convert the mv/v output of the load cell standard into engineering units.

OPTIONS AVAILABLE FOR MOREHOUSE CALIBRATING MACHINE The Morehouse Auxiliary Screw Pump is connected in series with the standard hand pump or optional Hydraulic Power Control used to control the

The Auxiliary Screw Pump is intended to provide more precise control, maintain load during calibration, and allow for more precise application of decreasing forces.

gear reduction unit, a hydraulic gage, and a manually operated vernier screw piston pump. The Power Control can be used with machines with capacities of 60,000 lbf and higher.

Call or write for Bulletin 260. LOAD CELLS Morehouse offers a series of calibration grade load cells with a range of performance specifications that include calibration in accordance with ASTM E74.

6 OPTIONS AVAILABLE FOR MOREHOUSE CALIBRATING MACHINE The Morehouse Auxiliary Screw Pump is connected in series with the standard hand pump or optional Hydraulic Power Control used to control the hydraulic jacks of Morehouse Universal Calibrating Machines. The Auxiliary Screw Pump is intended to provide more precise control, maintain load during calibration, and allow for more precise application of decreasing forces. The Morehouse Hydraulic Power Control is specifically designed with a low rate of flow to control the hydraulic jacks of Morehouse Universal Calibrating Machines. The Hydraulic Power Control consists of radial piston pump driven by an electric motor through a gear reduction unit, a hydraulic gage, and a manually operated vernier screw piston pump. The Power Control can be used with machines with capacities of 60,000 lbf and higher. OTHER MOREHOUSE EQUIPMENT PROVING RINGS The Morehouse Proving Ring is an accepted standard in the fi eld of force measurements. Its accuracy, repeatability and reliability are unsurpassed. Call or write for Bulletin 260. LOAD CELLS Morehouse offers a series of calibration grade load cells with a range of performance specifications that include calibration in accordance with ASTM E74. Call or write for Bulletin 302 DEAD WEIGHT FORCE MACHINE Morehouse Dead Weight Force Machines are true primary standards with unquestionable accuracy better than 0.002% (20 PPM) of applied load. Call or write for Bulletin 279 ACCREDITED FORCE CALIBRATION SERVICE Morehouse offers accredited force calibration services to 2,250,000 LBF (10,000,000 Newtons) in compression and 1,200,000 LBF (5,250,000 Newtons) in tension. Force calibrations through 120,000 LBF are performed using Morehouse Dead Weight (Primary Standards) Force Machines with weights calibrated directly by NIST. Force calibrations greater than 120,000 LBF are performed by comparison to secondary standards which have been calibrated directly by NIST.

Morehouse Instrument Company

Morehouse Instrument Company The Morehouse Universal Calibrating Machine is designed to use a compression force standard, proving ring or load cell to calibrate units under test in compression and tension. The reference standard and