Dytran 1051C Operating Manual

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Page 1

Dynamic Transducers and Systems

21592 Marilla St. • Chatsworth, CA 91311 • Phone 81 8-700-7818 www.dytran.com • e-mail: info@dytran.com

OG1051C.DOC 12-20-00 Rev A, ECN 9708, 03/06/13 Rev B, ECN 12897, 08/18/16

OPERATING GUIDE

MODEL 1051C

CHARGE MODE DYNAMIC FORCE SENSOR

This manual contains:

1) Outline/Installation drawing 127-1051C

2) Operating Instructions Model 1051C

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Rev B, ECN 12

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Page 3

-q V C

= -------- (Eq 1)

Where: V

is the output voltage (Volts)

q is the input charge, (pC) C

is the feedback capacitor, (pF)

This means that the sensitivity of the charge amplifier is determined by the value of the feedback capacitor only. Since the output voltage is fed back to the summing junction of the amplifier (the input terminal) the virtual input impedance is extremely high which means that the charge signal generated by the quartz crystals will not be drained away by the measuring device.

SIGNAL POLARITY Compressive forces on these sensors (see

Figure 1) produce negative-going output signals. This is because most charge amplifiers are inverting amplifiers and the output signal from the charge amplifier will be positive going for compressive loads. This is conventional.

By the same token, tension loads on the 1051C will produce positive-going output signals.

SENSITIVITY The nominal charge sensitivity of Model

1051C is -18 pC/Lb.

CHARGE AMPLIFIER SELECTION

Dytran manufactures many different types of charge amplifiers to suit the needs of most any measurement requirement from the larger laboratory type Model 4165 which features ranging and filtering plus standardization to the miniature in-line types 4751 and 4705 which adapt the 1051C to LIVM operation with constant current power units. For laboratory measurements, the 4165 is recommended and for field use, the dedicated sensitivity n-line charge amplifiers may be a better choice.

Consult the factory for recommendations on the best type of charge amplifier for your measurement needs.

INSTALLATION Refer to outline/installation drawing 127-

1051C, supplied with this guide. To mount model 1051C, it is necessary to

prepare a flat smooth mounting surface of 5/8” minimum diameter. The surface should be flat to .0005 TIR for best results.

The surrounding area must provide for room to connect the cable to the 10-32 connector at the end of the radial connector housing. Drill and tap a 1/4-28 hole to accept the model 6204 1/4-28 mounting stud. Thread in the mounting stud (supplied) to secure the 1051C to its mounting surface.

Before mounting the 1051C, thread the sensor into the mounting port and examine the fit of the mounting surfaces. They must meet parallel, i.e., a wedge must not be formed between these surfaces. Also, at this time, inspect the mating surfaces for foreign particles, which may become lodged between these surfaces and clean if necessary. It is important that the mating surfaces meet squarely and intimately with no particles of foreign matter of any kind included between them. Foreign particles included between mating surfaces could damage the sensor and/or modify the sensitivity of the sensor.

When you are satisfied that the surfaces are square and clean, place a thin layer of silicone grease on one of the surfaces and thread the force sensor place, torquing it in place with 25 to 30 Lbinches of torque to secure.

For most impact applications, the Model 6210S (steel) impact cap will be utilized. This cap is threaded into the platen (top surface of the force sensor). Thread this cap securely into the tapped hole in the platen, again inspecting for foreign particles between mating surfaces and clean if necessary. For more permanent installations, thread-locking compounds may be used to secure the installation. Use these compounds sparingly.

For a slightly higher resonant frequency, the aluminum cap, Model 6210A, may be a better choice in some applications.

Connect the sensor to the charge amplifier using Series 6010AXX cable (10-32 to 10-32) or Series 6011AXX (10-32 to BNC plug), depending on the connector called for by the power unit. Tighten

Rev B, ECN 12897, 08/18/16

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the cable lock ring snugly by hand. Do not use a pliers or vise grips on these cable lock rings.

OPERATION After connecting the cable from the sensor

to the charge amplifier, if the charge amplifier is the laboratory type, press the reset button which should zero the output voltage. You are now ready to select your range, set the discharge time constant and make the measurement.

If you are using an in-line charge amplifier, there is no reset button so you must wait a few seconds for the output voltage to stabilize. The instrument may be used before complete stabilization of the sensor bias voltage since the DC bias is blocked within the power unit.

Consult the factory for the low frequency limitations and other limitations when using the inline charge amplifiers.

LOADING CONSIDERATIONS, IMPACT When applying loads to the force sensor, it

is important to note that the load must be distributed evenly across the force sensitive face of the force sensor.

For impact measurements, the impact cap accomplishes this adequately in most cases. During impact testing, try to control the impact point so the contact occurs close to the center of the sensor. For more massive objects impacting the sensor, a special thicker cap may need to be employed. Consult the factory for special applications such as this.

Remember also, that the impact caps may be supplied in a variety of materials to suit the exact needs of the measurement. Call the factory to ask about the many different materials available, on special order, to meet your needs.

WRONG

OFF-CENTER LOADING

RIGHT

CENTRAL LOADING

STEEL BALL SPECIAL

ADAPTOR

FIGURE 3

ILLUSTRATING OFF-CENTER LOADING

Figure 3 is intended to illustrate the right and the wrong way to apply loads to the 1051C. Obviously we cannot address the many different applications but we merely want to illustrate, in the most basic sense, the proper and improper ways to apply loads to these instruments for the purpose of heading off measurement problems which may be incurred by improper use.

In the illustration chosen in Figure 3, a hydraulic or pneumatic ram is loading the force sensor dynamically. It is important that the force be evenly distributed, centrally, to the force sensor and the right way would be to use a steel ball to evenly load the sensor through a special adaptor which has been designed to center the ball over the force sensor.

Dytran offers such adaptors as a special order accessory. Our engineering department and our state of the art machine shop are at your disposal for the design and fabrication of such adaptors. Call the factory for assistance with your particular measurement problem.

TENSILE LOADING Figure 4 illustrates one proper way to load

the 1051C in tension. Again, the forces must travel through the center of the sensor.

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PROPER TENSILE LOADING

USING THREADED HOOK EYES

FIGURE 4

PROPER TENSILE LOADING

The arrangement shown in Figure 4 ensures that the load is applied centrally to the sensor without bending moments and transverse loading.

One important point to keep in mind when making tensile measurements is that, due to limits in the design of the internal preload structure of these sensors, the maximum tensile force is limited to

500 Lbs. in this series. If this level is exceeded, the sensor may be destroyed and the load will be suddenly released. This could engender dangerous

situations for personnel and equipment if this eventuality is not fully understood.

Remember that the maximum force is the combination of both static and dynamic tensile forces. For example, if the sensor is supporting a static load of 250 Lbs., the maximum dynamic range possible is 250 Lbs, (500 - 250).

QUASI-STATIC CONSIDERATIONS Close to DC measurements are possible

with the 1051C when used with a laboratory type charge amplifier such as the model 4165. These force sensors are calibrated at the factory by placing a traceable compressive force on them, (with a proving ring) then rapidly removing it and capturing the resultant step function on a digital storage oscilloscope. This is a very accurate and repeatable method for calibration of these sensors.

MAINTENANCE AND REPAIR The sealed construction of model 1051C

precludes field maintenance. Should you experience a problem with your sensor, contact the factory to discuss the problem with one of our sales engineers. If the instrument must be returned to the factory, you will be issued a Returned Materials Authorization (RMA) number so we may better follow the instrument through the evaluation process. Please do not return an instrument without first obtaining the RMA number. There is no charge for the evaluation and you will be notified of any charges before we proceed with a repair.

Rev B, ECN 12897, 08/18/16