Ortec AD811 Octal ADC

AD811 CAMAC Octal ADC Manual

DESCRIPTION

The AD811 Octal ADC contains eight peak-measuring analog-to-digital converters packaged in a single-width CAMAC module. The instrument is designed to measure positive unipolar or bipolar signals from nuclear shaping amplifiers in the range of 0 to +2 V. However, the circuit is completely dc-coupled and can be used for sampling dc or slowly changing voltages, allowing a wide range of applications.

The AD811 provides 1 mV resolution with a range of 11 bits (2047 counts) and a 12th bit is included in each of the eight data registers for overflow detection. The input linear gates and peak detectors are normally closed and the unit must be triggered by an external strobe pulse to start a conversion.

The strobe input pulse starts an internal gate width circuit that enables all eight linear gates and their peak detectors. The duration of the gate width is adjustable from 50 through 350 nSec with an internal control and can be set to overlap the peaks of the inputs for correct operation. The instrument has an excellent linearity and stability and is highly immune to crosstalk and power supply noise effects.

At the end of the gate interval, a conversion process starts and proceeds in parallel for all eight sections. The conversion lasts for approximately 80 uSec, independent of the input signal amplitude. At any time during this 80 uSec digitizing interval the conversion can be aborted by application of a signal to the front panel Clear input and the unit will be fully restored to its quiescent state within 0.5 uSec and be ready to accept another strobe.

At the completion of a normal conversion a LAM service request is generated and all accumulated data are held until they are reset from the Dataway control circuits. The busy and/or LAM status can be controlled at the module level by CAMAC commands in accordance with recommended practice.

Automatic testing and calibration checking of the module is accomplished by issuing the CAMAC command F25. An internal reference voltage is supplied to all eight converters and triggers a conversion. The reference voltage is sufficient to ensure overflow of all eight scaler-registers and a comparison of their measurements serves as a calibration check. This tests the analog circuits and the digital registers fully. A LAM service request is generated at the end of the conversion interval.

Two front panel indicators are included to monitor the status of the module. An "N" indicator shows when the AD811 is being addressed and remains lighted for one full second to ensure that it can be observed by the operator. A "B" indicator shows when the module is in a blocked condition and cannot accept a strobe to start a conversion. The blocked condition can be generated by either the internal busy latch or by a Dataway inhibit signal.

SPECIFICATIONS

INPUTS

Input 0 to 7

One input per channel accepts positive unipolar or bipolar signals with >50 nSec width in the positive lobe. Range 0 to >+2 V, peak measuring; protected to +/-5 V dc or +/-100 V transient; Z_in 1 K, dc-coupled.

Strobe

Accepts NIM-standard negative fast logic signal with >5 nSec duration to initiate conversion. The leading edge must precede the peak of the data signal by at least 80 nSec and the internal gate width must be adjusted to overlap the data signal peak. Protected to +/-5 V dc; Z_in 51 Ohm, dc-coupled.

Clear

Accepts NIM-standard negative fast logic signal with >5 nSec duration to abort a conversion and reset the logic and the scaler-registers. Must occur within 80 uSec after the trailing edge of the internally adjusted gate width for correct operation. Resets to <=0.1 % of full scale within 0.5 uSec. Protected to +/-5 V dc; Z_in 50 Ohm, dc-coupled.

OUTPUTS

Data

11 bits per section available on R1 to R11 Dataway lines. Overflow 1 bit per section (latching) available on R12 Dataway line.

LAM

Dataway LAM is set at the end of conversion; may be enabled/disabled and status-tested by CAMAC commands.

CONTROLS AND INDICATORS

Gate Width

An internal potentiometer controls the width of the gating signal, common to all eight sections, from 50 to 350 nSec. The strobe input leading edge should precede the data input peaks by at least 80 nSec, and the gate width control should be set to overlap the peaks for correct operation.

Calibrate

One internal potentiometer for each of the eight sections sets the calibration (slope) individually for its section.

Offset

One internal potentiometer for each of the eight sections adjusts a pedestal to correct the zero intercept individually for its section.

Enable/Disable I

An internal jumper-selectable Dataway Inhibit circuit.

B Indicator

Lights when unit is in a blocked condition.

N Indicator

Lights for 1 second when the unit is being addressed.

PERFORMANCE

Range

0 to >+2 V, peak measuring, into 2047 channels plus overflow.

Resolution

1.0 mV referred to input.

Channel Width

1.0mV/channel, 60% flat top profile.

Integral Nonlinearity

<= +/- 0.05%, 1% to 100% of full scale.

Differential Nonlinearity

<= 2%, 5% to 100% of full scale.

Conversion Time

Fixed at 80 uSec for all sections in parallel.

Crosstalk

A 5V signal with rise time >= 50 nSec will not affect any adjacent section by more than one channel.

Temperature Coefficient

<= +/- 0.025%/'C (0' to 50'C).

CAMAC CODES

F(0)-A(k)

(k = 0 to 7) Read selected register.

F(2)-A(k)

(k = 0 to 6) Read selected register.

F(2)-A(7)

Read register 7; clear all registers, busy, and LAM.

F(8)-A(12)

Test LAM; LAM = Q.

F(10)-A(12)

Clear LAM.

F(11)-A(12)

Clear all registers, busy, and LAM.

F(24)-A(12)

Disable LAM.

F(25)-A(k)

(k = 0 to 7) Test all registers. Measures a reference voltage in all sections that generates an overflow.

F(26)-A(12)

Enable LAM.

F(27)-A(12)

Test busy; busy = Q.

C

Clears all data registers, busy, and LAM status.

Z

Clears all data registers, busy, and LAM status, and disables LAM.

I

Inhibits operation of all sections (if accepted by jumper setting).

Q

Returned for all F-A function codes except F(8)-A(12) and F(27)-A(12) where the Q response is conditional.

X

Returned for all F-A function codes.

POWER REQUIRED

Maximum

+6V, 550 mA
-6V, 250 mA
+24V, 95 mA
-24V, 8 mA

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INPUTS
Input 0 to 7	One input per channel accepts positive unipolar or bipolar signals with >50 nSec width in the positive lobe. Range 0 to >+2 V, peak measuring; protected to +/-5 V dc or +/-100 V transient; Z_in 1 K, dc-coupled.
Strobe	Accepts NIM-standard negative fast logic signal with >5 nSec duration to initiate conversion. The leading edge must precede the peak of the data signal by at least 80 nSec and the internal gate width must be adjusted to overlap the data signal peak. Protected to +/-5 V dc; Z_in 51 Ohm, dc-coupled.
Clear	Accepts NIM-standard negative fast logic signal with >5 nSec duration to abort a conversion and reset the logic and the scaler-registers. Must occur within 80 uSec after the trailing edge of the internally adjusted gate width for correct operation. Resets to <=0.1 % of full scale within 0.5 uSec. Protected to +/-5 V dc; Z_in 50 Ohm, dc-coupled.
OUTPUTS
Data	11 bits per section available on R1 to R11 Dataway lines. Overflow 1 bit per section (latching) available on R12 Dataway line.
LAM	Dataway LAM is set at the end of conversion; may be enabled/disabled and status-tested by CAMAC commands.
CONTROLS AND INDICATORS
Gate Width	An internal potentiometer controls the width of the gating signal, common to all eight sections, from 50 to 350 nSec. The strobe input leading edge should precede the data input peaks by at least 80 nSec, and the gate width control should be set to overlap the peaks for correct operation.
Calibrate	One internal potentiometer for each of the eight sections sets the calibration (slope) individually for its section.
Offset	One internal potentiometer for each of the eight sections adjusts a pedestal to correct the zero intercept individually for its section.
Enable/Disable I	An internal jumper-selectable Dataway Inhibit circuit.
B Indicator	Lights when unit is in a blocked condition.
N Indicator	Lights for 1 second when the unit is being addressed.
PERFORMANCE
Range	0 to >+2 V, peak measuring, into 2047 channels plus overflow.
Resolution	1.0 mV referred to input.
Channel Width	1.0mV/channel, 60% flat top profile.
Integral Nonlinearity	<= +/- 0.05%, 1% to 100% of full scale.
Differential Nonlinearity	<= 2%, 5% to 100% of full scale.
Conversion Time	Fixed at 80 uSec for all sections in parallel.
Crosstalk	A 5V signal with rise time >= 50 nSec will not affect any adjacent section by more than one channel.
Temperature Coefficient	<= +/- 0.025%/'C (0' to 50'C).
CAMAC CODES
F(0)-A(k)	(k = 0 to 7) Read selected register.
F(2)-A(k)	(k = 0 to 6) Read selected register.
F(2)-A(7)	Read register 7; clear all registers, busy, and LAM.
F(8)-A(12)	Test LAM; LAM = Q.
F(10)-A(12)	Clear LAM.
F(11)-A(12)	Clear all registers, busy, and LAM.
F(24)-A(12)	Disable LAM.
F(25)-A(k)	(k = 0 to 7) Test all registers. Measures a reference voltage in all sections that generates an overflow.
F(26)-A(12)	Enable LAM.
F(27)-A(12)	Test busy; busy = Q.
C	Clears all data registers, busy, and LAM status.
Z	Clears all data registers, busy, and LAM status, and disables LAM.
I	Inhibits operation of all sections (if accepted by jumper setting).
Q	Returned for all F-A function codes except F(8)-A(12) and F(27)-A(12) where the Q response is conditional.
X	Returned for all F-A function codes.
POWER REQUIRED
Maximum	+6V, 550 mA -6V, 250 mA +24V, 95 mA -24V, 8 mA