BNC PB-5 User Manual

Instruction Manual - Rev. 4

Model PB-5

Precision Pulse Generator

Berkeley Nucleonics Corporation 2955 Kerner Blvd., San Rafael, CA 94901

Phone: [phone], Fax: [phone], Email: [e-mail], Web: www.berkeleynucleonics.com

	TABLE OF CONTENTS
SECTION 1. OPERATIONS		Page
1.1	Introduction	2
1.2	Principles of Operation	2
1.3	Function of Controls and Connectors	4
1.4	Menu Selections	5
1.5 Optimum Performance		6
1.6	Testing a Preamplifier	7
1.7	Measuring Differential Linearity of a MCA	7
SECTION 2. RS-232 COMMANDS		9
SECTION 3. PB5 HOST INSTRUCTIONS		11
3.1	What is PB5 HOST	11
3.2	Limitations	11
3.3	Hardware and Software Requirements	11
3.4	Installation and Setup	11
3.5	Toolbar Navigation	13
3.6 Command Format		14
3.7 PB5 HOST Command Summary		14
3.8	PB5 HOST Support	17
SECTION 4. SPECIFICATIONS		18

WARRANTY

Berkeley Nucleonics Corporation warrants all instruments, including component parts, to be free from defects in material and workmanship, under normal use and service for a period of one year. If repairs are required during the warranty period, contact the factory for component replacement or shipping instructions. Include serial number of the instrument. This warranty is void if the unit is repaired or altered by other than those authorized by Berkeley Nucleonics Corporation.

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SECTION 1

OPERATIONS

1.1 INTRODUCTION

The PB-5 sets a new standard for nuclear pulse generators. It offers full digital controllability with a built-in ramp generator. It provides tail and flat top pulses with excellent integral linearity and extremely low amplitude change with temperature. The PB-5 is capable of testing the stability, linearity and resolution of the most demanding spectroscopy circuits and instrumentation. It is the successor to the industry standard PB-4.

The PB-5 programmable precision pulse generator is menu-driven utilizing a 16-bit microcontroller. The front panel consists of a LCD display, keypad, and a spinner knob for selection of parameters and fine adjustments. A precision 16-bit DAC in conjunction with a 10-bit trim DAC is used to obtain excellent linearity and resolution over the 0 to 10 volt range. When driving 50 loads the output range is 0 to 5 volts (without affecting stability, linearity, or pulse shape). Temperature compensation is performed with an algorithm in software allowing precision (16-bit) settings and repeatability within ± 5 ppm/C°. Digital control is either manual or by RS-232 interface. Menu selections, such as saving/recalling pre-programmed configurations, provide many new features not previously available. The PB-5 will not require a separate ramp generator for linearity tests since it produces a digitally controlled linear ramp that will accurately test large multi-channel analyzers.

1.2 PRINCIPLES OF OPERATION

The block diagram is shown in Figure 1. A microcontroller (µ C) and its flash memory control the PB-5. The µ C receives external input commands from the keypad, spinner selector knob, RS-232 port, and temperature sensor readings. The µ C then converts these inputs to various codes that in turn drive the selected functions. When the unit is turned off the µ C stores the last settings of the pulser so that these settings can be recovered upon powering up the unit. It has the capability of storing an additional nine pulse settings for recall at any time. The amplitude is generated by a 16-bit serial DAC. The pulse is created by an electronic switch within the Pulse Amplitude circuitry. Next the pulse is shaped and fed to the Attenuator control which has a 50 series terminated output. The pulse parameters are shown to the user on a LCD display. These parameters are set by the keypad or by the spinner knob (optical encoder). The spinner has a push switch for enabling and selecting the user values. The spinner performs the same functions as the keypad but it is much easier to use. The keypad on the other hand allows a precise setting to be entered (e.g., amplitude 1.256750 volts for precision and repeatability).

The External Pulse Input passes through a limiter circuit and an adjustable level discriminator. The Input discriminator is controlled by a 10-bit serial DAC.

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FIGURE 1. Block Diagram of Model PB-5 Precision Pulse Generator

The Trigger Out Generator provides a pulse synchronized with the beginning of the reprate generator or the External Pulse Input. This provides synchronization with the target instrument.

The pulse Rep-Rate, Delay, and Width Generators are controlled by the Range Selector and the associated 10-bit DAC voltage. The pulse rise and fall times are selected via the µ C selector bus, providing shape control to the output amplifiers.

Temperature Sensor information is sent to the µ C which in turn operates the Temperature Trim DAC. Very fine adjustments (error corrections) are made to the amplitude every 5 minutes. When in the Ramp mode, corrections are made only between ramp cycles.

The RS-232 port provides connection to a computer from a remote location. All the functions can be remotely controlled by a PC running PB5 HOST program, a PC running HyperTerminal program, or by a standard terminal.

The pulse amplitude is set by a 16-bit DAC referenced to an accurate voltage source. A high-gain, low-drift amplifier buffers this voltage source. The output zero level is set by a zero-trim DAC controlling the buffer amplifier. During factory calibration the instrument is set so that the 0 to10 volt range can be adjusted within the precision specified (150 µ V). The output attenuator has ten selections that produce attenuation

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factors from 1 to 1000.

Factory testing and calibration is provided via an external tester. A multi-pin connector separates the µ C from the analog circuits. Normally they are connected together by this multi-pin plug. When the plug is removed a cable can be inserted from an external tester which provides the functions of the µ C. In conjunction with this mode of operation a test socket, connected to vital circuit points, collects data that can be used by an external test computer. The tester can automatically find the calibration points to be placed in the µ C memory.

1.3 FUNCTION OF CONTROLS AND CONNECTORS

The spinner knob is an optical encoder capable of slow or fast adjustments. Fine adjustments are made when the knob is rotated slowly. When the knob is rotated fast the parameter will change rapidly. Push the knob to make selections from the menu, rotate to desired value, and push again to select the value. To operate from the keypad, use the up/down keys and press the ENTER key to select.

The menu is easy to use since there are only two levels. To return to the main menu use the key on the keypad so marked, or push the spinner knob when in main menu position. One can use a combination of key pad and spinner knob or operate entirely with the spinner.

The ENTER key will allow sequential step selection of rise time, fall time, and attenuation. These are discrete values and therefore not entered with a specific value on the key pad (can also be selected with the spinner). Pulse amplitude is adjustable in increments of about 150 µ V (better than 1 part in 64,000). Since this amplitude adjustment is very fine it will take many turns of the spinner knob to cover the 0 to 10 volt range (even with fast rotation). Therefore, when covering a large amplitude range it may be expedient to enter the number with the keypad and then make any fine adjustments with the spinner.

The CLAMP mode is not a baseline restorer. Rather it allows long tail pulses to maintain the same amplitude as rep-rates exceed the duty cycle necessary for full exponential decay to the baseline. This is accomplished by clamping the tail to the baseline prior to the next pulse. This may be useful in some applications where the long tail must be preserved. For optimum performance in this mode the delay must be set greater than 3.0 µ s (see Section 1.5.4).

Three BNC connectors are located on the front panel. The PULSE OUT is reverse terminated in 50 and provides 0 to10 volts out (0 to 5 volts into 50 ). The EXT TRIG is used in conjunction with the menu to trigger the pulser at a given threshold and frequency up to 500 kHz. The TRIG OUT can be used to trigger a scope, another pulser, or system under test.

When remote operation is desired connect a null modem RS-232 cable to a PC running PB5 HOST program, a PC running HyperTerminal program, or to a standard terminal. From the main menu set the PB-5 to remote operation. For operation via PB5 HOST, refer to Section 3 of this manual. For operation via HyperTerminal select PROPERTIES from the HyperTerminal file menu to enter the following setup values):

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Hyper Terminal settings:

Flow control: None Data bits: 8 Emulation: VT 100 Parity: None

1.4 MENU SELECTIONS

Figure 2. shows the two level menu employed by the PB-5. The menu is selected by using the up/down keys on the keypad and pressing enter or by using the spinner/switch knob. Operating solely by the spinner is most convenient since rotating and depressing the push switch, all in one motion, makes the menu selection easy.

There are only two levels of menu selection - the main menu and the sub menu. There are 6 selections on the main menu: TRIGGER MODE, PULSE SETTINGS, RAMP SETTINGS, SCALE V/keV, SAVE/RECALL, and OPERATING MODE. The sub menu for each of these selections is shown separately in Figure 2. Four lines of information are displayed on the LCD at all times (represented by the dotted line in figure 2). The remaining items are viewed by scrolling up or down. The examples shown represent the maximum number of significant digits used in determining the parameter. For example, amplitude accuracy is given to 6 significant digits regardless of the decimal place (0.00001, 1.00000, 10.0000).

It should be noted that the least significant digit for amplitude might not give the same number with both the spinner knob and the keypad. Both methods of setting amplitude are accurate to at least 1 part in 64000, but if repeatability is desired the keypad should be used. (In the case of the spinner knob the µ C calculates the amplitude for every position and with the same accuracy as the keypad.)

Sub menu items are described in more detail directly below each sub menu. For example, discrete numbers for all rise time, fall time, and attenuation values are shown below the sub menu for the pulse settings. Note that many menu settings can be volts or keV. If using an isotope line for calibration in keV, the instrument will calculate equivalent volts so that value limits will not be exceeded. When the tail pulse is selected, rise time and pulse width are removed from the sub menu. This is because rise time is fixed at 50 ns and width is automatically set to minimum value in this mode. This insures the best accuracy and repeatability when using a tail pulse.

If there are circumstances that require different rise times, special tail pulses can be created in the flat-top mode (simply reduce the width to the minimum setting). The last item in the sub menu allows one to return to the main menu. Alternatively, the key marked "main menu" on the keypad will also allow a quick return to the main menu.

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