PCB PIEZOTRONICS 1403-13A (01) PDF Document

The specifications for the PCB PIEZOTRONICS 1403-13A are as follows:

When using the PCB PIEZOTRONICS 1403-13A, it is important to observe the following safety precautions:

• Failure of the load cell structure or fasteners used in the installation may cause personal injury and equipment damage.

• Provide adequate clearances and safety guards or shields properly surrounding test fixtures where fatigue-rated load cells are used.

• Review the manufactured data when selecting rod ends and fasteners for installation. Failure might occur due to a combination of measurement axis and extraneous loads if installation specifications are not followed.

• All test fixtures should be carefully evaluated for potential failure modes.

• Use threaded fasteners properly when assembling test fixtures. Fixtures with inadequately designed bolted joints or improperly tightened threaded fasteners can fail before the parts under test have completed the planned fatigue test cycles.

The general outline dimensions for the PCB PIEZOTRONICS 1403-13A and its related series are as follows:

The following optional components are available for the PCB PIEZOTRONICS 1403-13A and related series:

Note: The use of the tension base greatly increases the performance of the low profile load cell. Pre-tension studs include the threaded stud and the jam nut.

To mount the PCB PIEZOTRONICS 1403-13A to a standard or custom fixture, follow these steps:

1. The thickness of the new base or fixture must not be any thinner than the original base supplied with the load cell. Materials used must have the same temperature coefficient of expansion (for example, 4140 Steel).

2. The mounting surface must be flat (within 0.0002 inches), and steel fixtures must have a hardness of Rockwell C 38 to 42.

3. The threaded holes and under-head of the fasteners must be lightly lubricated with 30 weight oil or equivalent prior to tightening the mounting bolts.

4. Refer to the table below for the final tightening torque required for the bolt size used with your tension base.

5. Tighten the bolts in an incremental cross pattern with the following sequence: start with all bolts finger tight, followed by 25%, 50%, and finally 100% of the required torque being applied.

Tension Base Installation Torque Values

Note: To ensure catalog performance specifications are met, a customer’s supplied fixture or base must be flat to within 0.0002 inch and provide similar stiffness and hardness to a factory base.

Installation of threaded tension rods starts with pre-loading the load cell to 120-150% of its full-scale capacity. Lightly tighten a jam nut to lock in the preload on both the load cell and base tension rods. Once the preload tension is released, the threads will be securely engaged.

Important considerations:

• Failure to pre-load the attachment rods/fixtures can result in damage to the threads on the load cell and base during cyclic load tests.

• Threaded rods engaging the load cell should have Class 3 threads to ensure thread-to-thread close contact forces.

• The tension rods installed in the load cell and base must use full thread engagement but should not be jammed or torqued. They should be ½ to 1 turn from the bottom of the threads in both the base and load cell.

To mount the optional connector protector (Kit 084A90), follow these steps:

1. Remove the #4-40 x 1/4″ button head cap screws from the connector using a 1/16″ hex wrench.

2. Carefully pull the connector from the load cell. Take care not to break or loosen any wire connections.

3. Slide the connector protector (54823-02) behind the connector.

4. Apply a drop of Loctite® Threadlocker Blue 242® to the threads of the #4-40 x 3/8″ socket head cap screws. Refer to the Loctite® technical data sheet for directions of use.

5. Attach the connector protector to the load cell with the #4-40 x 3/8″ socket head cap screws using a 3/32″ hex wrench.

Kit Components (084A90)

Required Tools (Not Included)

The PCB PIEZOTRONICS 1403-13A is wired according to the Western Regional Strain Gage Committee Wiring Code, which uses a four-arm Wheatstone bridge configuration. The standard wiring is as follows:

• C: – Signal White

• D: – Excitation Black

• B: + Signal Green

• A: + Excitation Red

The typical wiring code for the standard PT02E-10-6P connector (Connector “A”) is:

• PIN A: +EXC

• PIN B: +SIG

• PIN C: -SIG

• PIN D: -EXC

• PIN E: N/C

• PIN F: N/C

Proper grounding and shielding are required to prevent electrical noise. The cable must be shielded twisted pairs with a drain wire. Cable shields must be grounded at only one end, for example, on the instrument or control system ground. The load cell case is grounded by mechanical attachment to the structure to which it is mounted.

The instrument or control system is grounded through its power cord. Ground loops and measuring system wiring may result in unstable or noisy signals.

A simple test with a voltmeter connected between the power cord ground and the structure on which the load cell is mounted can confirm that the structure has been properly grounded. If the power cord ground and structure ground are not at the same potential, it may be necessary to provide a secure structure ground, perhaps by driving a copper rod and attaching a ground strap.

The standard strain gage measurements are detailed below:

Side loads, moments, and torque must be limited to avoid electrical or mechanical damage to the load cell. The allowable extraneous loads are directly related to the rated capacity of the load cell:

• Maximum side force allowed is 100% of the rated capacity for the load cell.

• Maximum moment allowed is 100% of the rated capacity times 1 inch.

• Maximum torque allowed about the measurement axis is rated capacity times 1 inch.

Shunt calibration is used to simulate a known tension or compression load. To perform a shunt calibration, use the following procedure:

1. Stabilize all forces on the load cell. If possible, remove all loads.

2. Power up the host signal conditioner and connect it to the load cell via the appropriate cable, and allow for a 30-minute warm-up.

3. Set the load indicator display to read exactly 00.000.

4. Connect the shunt resistor to the terminals specified in the calibration certificate, and adjust the span or gain until the display reads the force value stated on the certificate.

5. Repeat steps 1-3 to verify that a valid calibration setting has been obtained.

6. If possible, apply a known load to the measurement system to further verify that the calibration has been accurately set up.

For the fatigue-rated 1400 series, a 60kΩ ± 0.01% precision shunt resistor simulates an output of approximately 73% of the full-scale output. The specific calibration values are found on the calibration certificates supplied with the load cell.

The following formula can be used to estimate the approximate value of the shunt resistor required to simulate a mechanical load:

Rcal = (25 * Rb) / (OutputFs * Lcal)

Where:

• Rcal = Shunt Resistor (K ohms)

• Rb = Bridge Resistance (ohms)

• OutputFs = Full Scale output of the load cell (mV/V)

• Lcal = Load to be simulated, % of Load Cell Capacity

Routine maintenance includes cleaning the electrical connectors, housings, and mounting surfaces with solutions and techniques that will not harm the physical material of construction. Caution should be observed to ensure that liquids are not permitted to migrate into devices that are not hermetically sealed. Such devices should only be wiped with a dampened cloth and never submerged or have liquids poured upon them. Never use a pressure washer on the load cells.

If the base has been removed for any reason, or the load cell has been mounted on a custom fixture without the base, it is a good idea to periodically test the mounting bolt tightness using a calibrated torque or click wrench.

Proper performance requires attention to both mechanical and electrical aspects. Follow these checklists for troubleshooting.

Mechanical Trouble Shooting

1. Check for proper installation of the load cell.

2. Check for properly tightened bolts.

Electrical Trouble Shooting

1. Check cables for proper wiring.

2. Inspect for loose or dirty electrical connections.

3. Check for improper shield grounds.

4. Check for proper grounding of the structure that the load cell is mounted on.

5. Check the signal conditioning electronics for proper setup.

6. Check the insulation resistance of shielded conductors for short circuits.

7. Check isolation resistance, load cell flexure to conductors.

8. Check load cell bridge resistances, (A-D) excitation and (B-C) the signal leads.

9. Check bridge balance.

10. Keep a record of your observations, correct problems, or contact the factory for assistance.

A load cell that has been severely overloaded will exhibit a significant zero offset. You can estimate the bridge unbalance using a digital ohm meter with a resolution of at least 0.1 ohm. Follow the Western Region wiring diagram to measure the resistances for each leg of the bridge (RAB, RAC, RDB, and RDC).

1. Estimate the Zero Offset (mV/V):

Zero Offset = 1.4 x (RAC – RAB + RDB – RCD)

2. Estimate the Bridge Unbalance (% Full Scale):

Bridge Unbalance = 100 x (Zero Offset / OutputFs)

Where:

OutputFs = Full Scale output of the load cell (mV/V)

A Zero Offset of greater than 10% indicates probable overload or possible fatigue damage. A load cell that has been significantly overloaded enough to create a large zero offset is not repairable.