from qolab.hardware.basic import BasicInstrument from qolab.hardware.multimeter import Multimeter from pyvisa import constants as pyvisa_constants import time class BK_5491(Multimeter): """BK 5491 multimeter Make sure to switch off the ECHO at the multimeter communication setup. Example ------- >>> rm = pyvisa.ResourceManager() >>> instr=rm.open_resource('ASRL/dev/ttyUSB0::INSTR') >>> multimeter = BK_5491(instr) >>> print("------ Header start -------------") >>> print(str.join("\n", multimeter.getHeader())) >>> print("------ Header ends -------------") """ def __init__(self, resource, *args, **kwds): super().__init__(*args, **kwds) self.resource = resource self.config["Device model"] = "BK 5491" self.resource.read_termination = "\r\n" self.resource.baud_rate = 9600 self.resource.data_bits = 8 self.resource.parity = pyvisa_constants.Parity.none self.resource.stop_bits = pyvisa_constants.StopBits.one self.resource.timeout = 5000 self.read = self.resource.read # we need to work around the prompts which BK_5491 sends during # communication to mimic SCPI # if you need raw connection use self.resource.write or self.resource.query # self.write = self.resource.write # self.query = self.resource.query self.read_bytes = self.resource.read_bytes self.read_binary_values = self.resource.read_binary_values self.query_binary_values = self.resource.query_binary_values self.switchTime = 0.5 # switch time in seconds for Function/Measurement change self.deviceProperties.update({"Function"}) def isPrompt(self, string): if string[1] == ">": return True return False def isPromptGood(self, prompt): if prompt[0:2] == "=>": return True print(f"Error detected {prompt=}") return False def write(self, cmd_string): """Write/send command to instrument""" return self._readwrite(cmd_string, expect_reply=False, Nattemts=1) def query(self, cmd_string): """Query instrument with command""" return self._readwrite(cmd_string, expect_reply=True, Nattemts=5) def _readwrite(self, cmd_string, expect_reply=True, Nattemts=5): """ Send command to instrument or query it readings (which is also a command) BK_5491 is not a SCPI instrument, so we get some replies (prompts *>, =>, etc) even if we just send a command not a query. So we have to work around this. """ self.resource.read_bytes(self.resource.bytes_in_buffer) # clear read buffer # print(f"dbg: {cmd_string=}") self.resource.write(cmd_string) if expect_reply: reply = self.resource.read() # this should be result # print(f"dbg: {reply=}") if self.isPrompt(reply): prompt = reply if prompt[0] == "@": if Nattemts >= 2: # print('dbg: numeric reading is not available yet, attempt one more time') time.sleep(self.switchTime) return self._readwrite( cmd_string, expect_reply=expect_reply, Nattemts=Nattemts - 1 ) print( f'Error: we ask {cmd_string=} and got prompt "{reply}" instead of result' ) return None else: reply = None prompt = self.resource.read() # this should be prompt if not self.isPromptGood(prompt): print(f'Error: expected good prompt but got "{prompt=}"') return reply def getReading(self): """Report current measurement displayed on the first/main display""" ret_string = self.query("R1") # print(f'dbg: getReading received "{ret_string}"') return float(ret_string) """ BK_5491 has two displays which could be set and read separately, here we use only setting of the 1st display (prefix S1 below) to set the measurement and read it later. It is also possible to set range, but I prefer to leave in to the front panel user. If this is needed it would be followed by 3 symbols specifiers as outline in the manual. """ @BasicInstrument.tsdb_append def getVdc(self): self.write("S10") return self.getReading() @BasicInstrument.tsdb_append def getVac(self): self.write("S11") return self.getReading() @BasicInstrument.tsdb_append def getAdc(self): self.write("S14") return self.getReading() @BasicInstrument.tsdb_append def getAac(self): self.write("S15") return self.getReading() @BasicInstrument.tsdb_append def getResistance(self): self.write("S12") return self.getReading() @BasicInstrument.tsdb_append def getResistance4Wires(self): self.write("S13") return self.getReading() @BasicInstrument.tsdb_append def getDiode(self): self.write("S16") return self.getReading() @BasicInstrument.tsdb_append def getFreq(self): self.write("S17") return self.getReading() """ With BK_5491 It is possible to send "key presses" like they are coming from the front panel K1 - Vdc K2 - Adc K3 - Vac K4 - Aac K5 - Resistance K6 - Diode K7 - Frequency (Hz) K8 - Auto K9 - Up key K10 - Down key K11 - MinMax key K12 - Hold key K13 - Local (manual does not specify, but it works this way) K14 - Rel key K15 - Shift key K16 - 2nd key K17 - Vdc and Vac keys simultaneously K18 - Adc and Aac keys simultaneously K19 - Shift then Up keys (increasing the intensity of the VFD display) K20 - Shift then Down keys (decreasing the intensity of the VFD display) """ def toLocal(self): self.sendCmd("K13", expect_reply=False) def getFunction(self): reply = self.query("R0") """ According to the manual: The reply is in 10 digits in the form

the and correspond to measurement/function of the 1st and 2nd display. Looks like it some sort of a lie, since in our BK_5491A with firmware v1.23,3 we get back either 11 digits (if both displays are on) or 9 if only 1st display is on. We are concerned with 1st (primary) display """ if len(reply) == 9: f1 = reply[7] elif len(reply) == 11: f1 = reply[7] else: return "Unknown" print(f1) if f1 == "0": return "Vdc" elif f1 == "1": return "Vac" elif f1 == "2": return "Resistance" elif f1 == "3": return "Resistance4Wires" elif f1 == "4": return "Adc" elif f1 == "5": return "Aac" elif f1 == "6": return "Diode" elif f1 == "7": return "Frequency" elif f1 == "8": return "V(ac+dc)" elif f1 == "9": return "A(ac+dc)" elif f1 == "A": return "Continuity" else: return "Unknown" if __name__ == "__main__": import pyvisa print("testing") rm = pyvisa.ResourceManager() print(rm.list_resources()) instr = rm.open_resource("ASRL/dev/ttyUSB0::INSTR") multimeter = BK_5491(instr) print("------ Header start -------------") print(str.join("\n", multimeter.getHeader())) print("------ Header ends -------------")