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42.1 GENERAL DESCRIPTION . . . . . . . . . . . . . . 42-1
42.2 ANALOG INPUT SPECIFICATIONS . . . . . . . . . . 42-3
42.3 PERFORMANCE SPECIFICATIONS . . . . . . . . . . . 42-3
42.3.1 Ranges . . . . . . . . . . . . . . . . . . . . 42-3
42.3.2 DC Resolution . . . . . . . . . . . . . . . . 42-3
42.3.3 Temperature . . . . . . . . . . . . . . . . . 42-3
42.3.4 DC Accuracy . . . . . . . . . . . . . . . . . 42-4
42.3.5 AC Measurement . . . . . . . . . . . . . . . . 42-4
42.3.6 Power Supply Requirements. . . . . . . . . . . 42-4
42.4 DATA PROCESSING (RELEASE 1) . . . . . . . . . . 42-4
42.4.1 Calibration . . . . . . . . . . . . . . . . . 42-4
42.4.2 Digital Filter (DC) . . . . . . . . . . . . . 42-5
42.4.3 Channel Refresh Rate. . . . . . . . . . . . . 42-5
42.4.4 AC Measurements . . . . . . . . . . . . . . . 42-6
42.4.5 Range Information . . . . . . . . . . . . . . 42-6
42.5 CAMAC COMMANDS AND RESPONSES. . . . . . . . . . 42-7
42.5.1 System Reset . . . . . . . . . . . . . . . . . 42-7
42.5.2 Command Register . . . . . . . . . . . . . . . 42-7
42.5.3 Channel Starting Address . . . . . . . . . . . 42-7
42.5.4 Channel Read . . . . . . . . . . . . . . . . . 42-7
42.5.5 X Response . . . . . . . . . . . . . . . . . . 42-8
42.5.6 Q Response . . . . . . . . . . . . . . . . . . 42-8
42.6 FRONT PANEL LAYOUT . . . . . . . . . . . . . . . 42-8
42.6.1 'OK' LED . . . . . . . . . . . . . . . . . . . 42-8
42.6.2 'X' LED . . . . . . . . . . . . . . . . . . . 42-8
42.6.3 Analog Input Connectors . . . . . . . . . . . 42-8
42.7 CAMAC COMMAND SUMMARY . . . . . . . . . . . . . 42-9
42.8 ANALOG CONNECTOR PIN-OUT . . . . . . . . . . . . 42-10
42.9 FLOATING POINT FORMAT . . . . . . . . . . . . . 42-11
42.9.1 VAX Single Precision Floating Point Format . . 42-11
42.9.2 IEEE Single Precision Floating Point Format. . 42-11
42.10 DRAWING PACKAGE NUMBER . . . . . . . . . . . . . 42-12
42.11 RESPONSIBLE ENGINEER . . . . . . . . . . . . . . 42-12 CHAPTER 42 SMART ANALOG MONITOR (SAM)
42.1 GENERAL DESCRIPTION The Smart Analog Monitor (SAM) (#123-603) is a single width CAMAC module having thirty two differential channels of slow analog to digital conversion controlled by an internal microprocessor. Ranging, polarity and calibration are fully automatic. The data output format is floating point in units of volts. The microprocessor circulates through the 32 input channels, measuring the DC voltage for each channel and storing the results in the CAMAC output buffer. The measurement process consists of range and polarity acquisition, digital signal averaging over one 60 Hz period to remove normal mode AC, gain and offset correction, and conversion of the data to floating point format. Periodically the processor calibrates the module and makes measurements of the normal mode AC signal component on each channel. The range and AC measurement are encoded into the least significant byte of the floating point word; they do not significantly affect the floating point number representation of the DC voltage. The pin assignment for the front panel connectors is given in Figure 1. The floating point output word is illustrated in Figure 2. The processor first acquires the sign and range of a channel by basically requiring the ADC to be operating in the upper half of its range. If this condition is not met at any time during the signal averaging process, the gain and/or polarity is corrected and the averaging restarted. The digital filtering process,for the slow scan mode, consists of averaging 64 equally spaced readings over 1/60th of a second as determined by the internal crystal clock. Normal mode rejection at 60 Hz and its harmonics is at least 35DB. The 'fast' scan mode averages 8 readings in 2 milliseconds and does not provide 60 Hz rejection. This mode is provided for 'tweeking' purposes. This unit extends the resolution of an inexpensive 12 bit ADC to 14 bits by 'dithering' the ADC's analog input. Dithering is accomplished by injecting the scaled output of a 4 bit DAC into the ADC and stepping the DAC each time an ADC sample is taken. The DAC's most significant two bits are scaled to over-lap the ADC's two least significant bits and the remaining two DAC bits represent the 13th and 14th bits of the ADC. Combining this with the filtering process, as
SMART ANALOG MONITOR (SAM) Page 42-2 previously described, removes the quantizing error of the 12 bit ADC and extends the resolution to 14 bits. The processing time per channel, in the normal scan mode is 20 ms, consisting of 16 ms for the digital filtering and 4 ms for correction and formatting. Thus, the total refresh interval for the module is0.64 seconds if no ranging or polarity changes occur. The refresh in fast mode is 0.12 seconds. During calibration and AC measurement, the DC data is not being refreshed. This is indicated by X=0 if a read is made during this time. The data from the previous read is still valid and available in the buffer. The analog input electronics incorporates a Programmable Gain Instrumentation Amplifier (PGIA) whose voltage range (R) can be changed in 11 binary weighted steps from 10.24 volts through 10mV. R is an integer whose value may be 0 through 10, and is stored in the range nibble of the output word. This information is useful for determining the resolution V[res], and the full scale voltage V[fs] of a given input signal. V[res] = Vinput(2**-14)(2**-R). V[fs] =
10.24(2**-R). The micro-processor applies a linear calibration correction to each reading. The coefficients are obtained from a calibration procedure that measures offset values for each gain range of the PGIA and an overall system gain (effectively the gain of the internal ADC). This procedure assumes the the internal voltage reference (REF), has been accurately adjusted to 10.240 volts, and the gain precision of the PGIA is better than 0.02%. The calibration procedure is performed every two minutes. The full scale range is S[R] = REF/2*R,yielding ranges between 10.24V and 10.00 mV. The system gain G = Vadc[REF]-bo, where Vadc[REF] is the ADC response to the REF, and bo is the ADC response to a shorted input. Both reading have R = 0. The corrected channel is then: V[x] = S[R]/G*(Vadc[x]-b[R]). Vadc[x] is the digitized value of input x through the PGIA set to range R and b[R] is the ADC response for a shorted input channel on various ranges of the PGIA. AC measurements are made every two minutes only in the normal scan mode. The intention, in this software release, is to check for "contaminating" AC on the DC level. For example, if the channel is measuring the shunt voltage on a magnet power supply, the AC measurement will check for a ripple component arising from a damaged filter section. The measurement records the maximum peak to peak excursion of the input voltage during the signal processing time of 1/60th second. The encoded value (N), is stored in the AC nibble of the output word. N is in the range of 0 through 12. The encoding of N is the integer portion of log[2]*800(2**(V[p-p])) @ 60 Hz. Due to the normal mode input filter, the sensitivity decreases 6DB/octave above 60Hz. N may vary between 0 and 1 for a clean DC signal due to the algorithm used. Therefore, values of N > 1 are significant. The sensitivity of the AC measurement is 0.2% of the DC voltage at 60 Hz. The accuracy is +20/-100%.
SMART ANALOG MONITOR (SAM) Page 42-342.2 ANALOG INPUT SPECIFICATIONS o Thirty two differential channels. o DC input impedance twenty meg-ohm. o Passive common mode low pass filter response is -3DB @ 10 KHz. o Maximum continuous DC voltage is 40 volts. o Maximum DC voltage for one second is 100 volts. o Input voltage, normal mode plus common mode, must be less than 10.3 volts for specified accuracy. o Common mode rejection between 0 and 60 Hz is 80 DB minimum. o Maximum source impedance, normal mode, is 2K ohm for specified accuracy. o Maximum source impedance, common mode imbalance, is 100 ohm.
42.3 PERFORMANCE SPECIFICATIONS
42.3.1 Ranges o +/- 10 mV to +/- 10.24 volts full scale in steps of 2X. o Maximum voltage difference between channels must be less than 40 DB for specified accuracy.
42.3.2 DC Resolution o Monotonic to 14 bits.
42.3.3 Temperature o Module will maintain specified accuracy between 0 and 50 degree Celsius.
SMART ANALOG MONITOR (SAM) Page 42-442.3.4 DC Accuracy o 0.05% of reading +/- 20 micro-volts on all ranges for the normal scan mode. o 0.2% of reading +/- 40 micro-volts on all ranges for the fast scan mode. o 0.01% of reading per month.
42.3.5 AC Measurement o Resolution is 0.2% of DC voltage @ 60Hz. Sensitivity decreases 6DB/octave above 60Hz. o Accuracy is +20/-100% of reading.
42.3.6 Power Supply Requirements. o +6 volts @ 900 mA. o +24 volts @ 40 mA. o -24 volts @ 40 mA.
42.4 DATA PROCESSING (RELEASE 1)
42.4.1 Calibration Calibration is performed by the micro-computer using linear correction. Two assumptions are made using this scheme: One, the on board reference supply is adjusted correctly and two, the Programmable Gain Instrumentation Amplifier (PGIA) meets its 0.02% accuracy specification. Every two minutes the 10.24 and zero volt references are digitized. The values of the zero volt reference for each gain setting of the (PGIA) are maintained in a look-up table. Offset correction is performed by subtracting the appropriate value from the digitized channels. The gain correction factor is determined from the value read on the 10.24 reference channel. The offset is removed from this channel and 10.24 is divided by this result. Each channel is multiplied by this correction constant.
SMART ANALOG MONITOR (SAM) Page 42-5 Mathematically........ S[R] = 10.24(2**-R). G = Vadc[REF]-bo. bo = Vadc(0) for range R. V[x] = S[R]/G(Vadc[x]-b[R]). Where: R = Range setting of the PGIA. S = Full scale voltage range. G = System gain. REF = Reference supply (10.240 volts). b = Offset. x = Channel number. V = Voltage.42.4.2 Digital Filter (DC) o Normal scan mode. Each channel is averaged, normal mode, over 1/60 th of a second as determined by the internal crystal. Sixty four samples are accumulated then divided by sixty four. Normal mode rejection at 60 Hz and its harmonics is 35 DB minimum. o Fast scan mode. Each channel is averaged, normal mode, over eight samples. No 60 Hz rejection is provided.
42.4.3 Channel Refresh Rate. o Normal scan mode. Each channel requires 20 milliseconds for processing. The 20 milliseconds include 16 milli-seconds for averaging, and 4 for data correction formatting. Total refresh rate for the 32 channels is therefore 640 milliseconds.
SMART ANALOG MONITOR (SAM) Page 42-6 The worst case refresh time is 2 seconds if all 32 channels see a large input step and polarity reversal. o Fast scan mode. Each channel requires 4 milliseconds for processing. Total refresh rate for the rate for 32 channels is 120 milliseconds.42.4.4 AC Measurements Provided only in the normal scan mode. o Once every 2 minutes, the normal mode AC signal components are measured and recorded. The measurement records the maximum peak to peak excursion of the input voltage during the signal processing time of 1/60th second. o The encoded value (N) is stored in the AC nibble in the output word. o The encoding is the integer portion of log[2](800(2**R(V[p-p]))) @ 60 Hz. N is in the range of 0 through 12. R = PGIA range value. V[p-p] = peak to peak input voltage.
42.4.5 Range Information Gain range information is provided in the range nibble (R), of the output word. R is in the range of 0 to 10. The full scale voltage is
10.24/(2**R).
SMART ANALOG MONITOR (SAM) Page 42-742.5 CAMAC COMMANDS AND RESPONSES.
42.5.1 System Reset System reset is accomplished with F9.
42.5.2 Command Register F16 loads the processor command register. o W8 - W1 is read by the processor. o W1= Request firmware revision number.The number is returned to all channels in floating point format. This bit must be cleared for analog processing to continue. o W2= Request fast scan mode. No AC processing will be provided in this mode. o W3= Request IEEE floating point format.
42.5.3 Channel Starting Address Channel starting address is set by F17 with W5-W1 supplying channel number. The reads following the F17 command must occur at least every 75 milliseconds to insure proper channel acquisition. After a major read, i.e., a block transfer, 200 milliseconds should be allowed for the micro-processor to update the CAMAC buffer. In other words, the micro is prevented from updating the CAMAC buffer for a period of 100 milliseconds every time the module is accessed.
42.5.4 Channel Read Outputs are stored in double buffered fast memory which is read and incremented by F0. Each read produces 16 bits of a 32 bit word for each channel. o All channels will be set to greater than 90 volts if the previous calibration was unsuccessful. o An individual channel will be set to greater than 90 volts if it can not be digitized. Floating inputs or large oscillations may cause this to happen.
SMART ANALOG MONITOR (SAM) Page 42-842.5.5 X Response o X = 1 if a valid command is issued and the processor is not doing AC measurements or calibration, and the previous calibration was successful. o Front panel 'X' LED means valid command.
42.5.6 Q Response Q = 1 if an F0 is issued and the processor is updating CAMAC buffer and the channel address is in the range of 0 to 31 and channel reads occur a least every 75 milliseconds for a scan operation. This feature permits "Q scans" across groups of SAM's.
42.6 FRONT PANEL LAYOUT
42.6.1 'OK' LED The 'OK' LED blinks at one half channel refresh rate if the previous calibration was successful.
42.6.2 'X' LED The 'X' LED implies a valid CAMAC command was issued.
42.6.3 Analog Input Connectors o Two 36 pin AMP connectors, #204731-2, are provided for the analog inputs. o There are sixteen differential channels per connector. o There is one group shield per connector. o The 10.240 volt reference through 5k ohm and it's return is on each connector. o There is one analog return per connector. o There is one reference return per connector.
SMART ANALOG MONITOR (SAM) Page 42-942.7 CAMAC COMMAND SUMMARY o F9 - Processor reset. o F16 - Load control register (W8-W1). W1 - firmware revision number W2 - Fast scan mode W3 - IEEE floating point format o F17 - Set starting channel number (W5-W1). o F0 - Sequential read the channels starting from the one set by F17. Two reads per channel. Data presented to R16-R1. o X returned for any valid command and not performing calibration or AC measurements, and the previous calibration was successful. o Q returned for F0 and the fast RAM is being refreshed and current channel number does not exceed 31 and the channels are being read at a 75 millisecond rate or faster. There must be a 200 millisecond pause between block transfers to allow the micro-processor to update the CAMAC buffer.
SMART ANALOG MONITOR (SAM) Page 42-1042.8 ANALOG CONNECTOR PIN-OUT CONNECTOR LOGIC TRUE LOGIC FALSE CHANNEL J2 J3 0 16 A1 A2 1 17 A3 A4 2 18 A5 A6 3 19 A7 A8 4 20 A9 A10 5 21 A11 A12 6 22 B1 B2 7 23 B3 B4 8 24 B5 B6 9 25 B7 B8 10 26 B9 B10 11 27 B11 B12 12 28 C1 C2 13 29 C3 C4 14 30 C5 C6 15 31 C7 C8
10.240 VOLT REFERENCE through 5.1k 1% resistor C9
10.240 VOLT RETURN C10 ANALOG RETURN C11 GROUP SHIELD C12
SMART ANALOG MONITOR (SAM) Page 42-1142.9 FLOATING POINT FORMAT
42.9.1 VAX Single Precision Floating Point Format (Software release 1) FIRST CAMAC READ |R R R|R R R| |1 1 | | |6 5 9|8 7 1| +------------------------+---------------------+ |S|<----- EXPONENT ------->|<-- MS FRACTION -->| |I |G |N SECOND CAMAC READ |R R|R R|R R| |1 | | | |6 9|8 5|4 1| +------------------------+---------+-----------+ |<----- LS FRACTION ---->|
|<- RANGE ->| 42.9.2 IEEE Single Precision Floating Point Format. (Software release 1) FIRST CAMAC READ |R R|R R|R R| |1 | | | |6 9|8 5|4 1| +------------------------+---------+-----------+ |<----- LS FRACTION ---->|
|<- RANGE ->| SECOND CAMAC READ |R R R|R R R| |1 1 | | |6 5 9|8 7 1| +------------------------+---------------------+ |S|<----- EXPONENT ------->|<-- MS FRACTION -->| |I |G |N
SMART ANALOG MONITOR (SAM) Page 42-1242.10 DRAWING PACKAGE NUMBER 123-603
42.11 RESPONSIBLE ENGINEER D. J. Nelson